Mineral-based porous sand and methods for making mineral-based porous sand

ABSTRACT

A method for manufacturing a mineral-based porous granular material includes providing a starting material of at least 70 weigh % of an micaceous arkose rock material. The starting material is in a granular form having at least 50 volume % with a mean diameter of between about 0.060 mm and about 0.65 mm. The method includes placing the starting material into a bed on a support surface, placing the support surface containing the bed of the starting material into a kiln, and subjecting the bed of starting material within the kiln to a basic processing temperature of between about 1100° C. and about 1300° C. for a basic processing temperature processing time selected to transform at least 40 volume % of micaceous components in the micaceous arkose material into feldspar, and to evolve at least 30 volume % of metal sulfides within the feldspar from the feldspar as metallic oxides.

BACKGROUND

In certain instances it is desirable that rainwater and the like drainquickly from a surface area covered by paving tiles. In certain uses itis desirable that the water quickly drain through the pavers (in whichcase a high permeability is desired). In other instances it is desirablethat the water be retained within the pavers and slowly released throughdrainage and/or evaporation. One example where this latter feature isdesirable is in managing storm water. In this instance it can be furtheradvantageous that the pavers provide a filtering function to removeparticulate matter and other pollutants from the storm water. Sincestorm water typically is routed to sewer systems via storm drains, stormwater and pollutants contained therein can place a significant burden onsewage treatment facilities. It is thus desirable to reduce the volumeof storm water flowing into storm drains, and also to removecontaminates from the storm water before it enters the storm drains. Itis further desirable that filler material (such as sand and gravel)beneath and between pavers and the like also be able to retain a largevolume of water and release the water slowly. In addition to filteringstorm water, it is also desirable to provide a durable porous materialthat can be used to filter air and other liquid and gas flows.

It is also desirable to be able to form unitized building materials (asfor example, bricks, pavers, beams, unitized slabs and other buildingmaterials) having high strength, but that do not require significantamounts of cement in their formation. That is, it is desirable to reducethe amount of cement required in forming such unitized buildingmaterials. At least in the U.S., the Portland cement manufacturingindustry is becoming increasingly regulated (e.g., by the U.S.Environmental Protection Agency at the U.S. Federal level) to reduceemissions of toxic air pollutants, such as mercury, acid gases, carbondioxide, and total hydrocarbons, along with emissions of particulatematter, which are typically generated during the manufacture of cement.

It is additionally desirable to provide an alternative to clay-basedbricks which combine structural and architectural elements, and whichcan be kilned in a time period shorter than the typical clay-based brickkilning period (commonly about 24-48 hours), thus reducing energyconsumption and environmental pollutants (such as carbon dioxide)frequently associated with energy generation.

It is further desirable to provide unitized building materials, and inparticular, such materials used in walkways and roadways, that arechemically resistant to ice melting chemicals and other materials thatmay be applied atop of the unitized building materials. Still further,in certain applications it is desirable that unitized building materialsbe light weight, yet still retain the strength required for theirintended use. It is also desirable to achieve higher strengths(compressive and/or tensile) in unitized building materials, as well asincreased resistance to stresses imposed by freezing and thawing ofwater that can be entrained within the unitized building materials.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of an exemplary method for manufacturing a porousmineral-based granular material, according to the present disclosure.

FIG. 2A is the first part of a two-part flowchart (which is continued onFIG. 2B) of an exemplary method for manufacturing a unitized formedconstruction material, according to the present disclosure.

FIG. 2B is the second part of a two-part flowchart (which is acontinuation from FIG. 2A) of an exemplary method for manufacturing aunitized formed construction material, according to the presentdisclosure.

FIG. 3 is a sectional side view of a unitized formed constructionmaterial, a reinforcing bar member, and an envelope of felsic materialsurrounding the reinforcing bar member.

FIG. 4 is a sectional plan view of a mold which contains a mixture ofthe starting materials for a unitized formed construction material, andincluding hole-forming metal bar material used to form holes forinstallation of post-kilning reinforcing bar material.

FIG. 5 is a partial side sectional view depicting a surface coveringsystem that includes permeable tiles inserted in and through a generallyimpermeable surface covering.

FIGS. 6 and 7 are partial side sectional views depicting variations ofthe surface covering system of FIG. 5.

FIG. 8 is a plan view depicting a variation of the surface coveringsystem of FIG. 5, and including permeable tiles that interlock with theadjacent generally impermeable surface covering.

FIG. 9 is partial side sectional view depicting another variation of thesurface covering system of FIG. 5.

FIG. 10 is a partial side sectional view depicting another surfacecovering system that includes permeable tiles inserted in and through agenerally impermeable surface covering.

FIG. 11 is a partial plan view of the surface covering system depictedin FIG. 10.

DETAILED DESCRIPTION

The following disclosure provides (without limitation) my discovery ofmethods for manufacturing mineral-based porous granular materials, aswell as such manufactured mineral-based porous granular materials. Themineral-based porous granular materials provided for herein can be usedas subgrade fill material, as a soil additive, as a filter material, andcan also be used in the manufacture of unitized building materials(among other uses not specifically described). The following disclosurealso provides (without limitation) for methods for manufacturingmineral-based unitized building materials (as well as for themineral-based unitized building materials themselves) that reduce thequantity of cement required over current methods for manufacturingmineral-based unitized building materials. The mineral-based unitizedbuilding materials provided for herein can be engineered (as providedfor below) to accommodate at least desired properties of porosity,permeability, chemical resistance, air entrainment, strength anddensity.

The following disclosures are generally directed towards mineral-basedporous granular materials and mineral-based unitized building materials,while allowing for certain variations. The term “mineral-based” is usedherein to refer to base materials that are composed of more than fiftypercent by weight (50 weight %) of elements having atomic numbersgreater than 10 (an atomic number of 10 being associated with theelement neon, and an atomic number of 11 being associated with theelement sodium). That is, mineral-based materials (as the term is usedherein) exclude hydrocarbon-based materials (i.e., materials that arecomposed of more than fifty percent by weight (50 weight %) of elementshaving atomic numbers of less than 11, and specifically materialsprincipally composed of carbon, hydrogen and oxygen.

As a general rule, when hydrocarbon-based materials are subjected totemperatures in excess of about 650° C. (about 1200° F.) thehydrocarbon-based materials tend to either vaporize or fuse into aconsolidated block having low porosity and low permeability. (Anyporosity of hydrocarbon-based materials subjected to a temperature inexcess of about 650° C. is largely in the range of about 5 microns orgreater as the result of the inclusion of gaseous bubbles, accompaniedby low permeability.) By comparison I have discovered that whenmineral-based materials are subjected to temperatures in excess of about650° C. (about 1200° F.) they tend to form porous materials due to theevolution (including sublimation and/or vaporization) of chemicalcompounds from the initial mineral-based materials.

The following disclosure will be generally discussed in two parts: (i)methods for manufacturing mineral-based granular materials (includingmineral-based porous granular materials); and (ii) methods formanufacturing mineral-based unitized building materials (includingmineral-based porous unitized building materials, and especiallyfluid-permeable mineral-based unitized building materials).

Mineral-Based Porous Granular Materials.

In the following discussion I will, from time-to-time, refer to thegranular materials (both starting materials and finished materials) asbeing associated with a particular grade of sand. Different grades ofsand are defined by recognized standards, such as the by the AmericanAssociation of State Highway and Transportation Officials (“AASHTO”),the American Society for Testing Materials (“ASTM”), and theInternational Organization for Standardization (“ISO”). Specifically,AASHTO M 145, ASTM D3282, and ISO 14688 provide for the definitions ofdifferent grades of sand. More specifically, the following grades ofsand may be referred to herein: (i) fine sand, being between 0.063 mmand 0.2 mm per ISO 14688, and between 0.125 mm and 0.250 mm per AASHTO M145; (ii) medium sand, being between 0.2 mm and 0.63 mm per ISO 14688,and being between 0.250 mm and 0.50 mm per AASHTO M 145; and (iii)course sand, being between 0.63 mm and 2.0 mm per ISO 14688, and beingbetween 0.50 mm and 1.0 mm per AASHTO M 145. (AASHTO M 145 furtherdefines very coarse sand as being between 1.0 and 2.0 mm.) It will beappreciated that the sizes referenced are mean diameters, and aremeasured by passing the sand material through a first sieve to separateparticles smaller than the lower end of the size range, and then passingthe remaining materials through a second sieve to separate particlesgreater than the higher end of the size range. The remaining particlesthus essentially fall within the size range designated for the grade ofsand (or sand grade). As can be appreciated, there is some overlap inthe above definitions of sand grades (e.g., between ISO 14688 and AASHTOM 145). Accordingly, in the following discussion I will use thefollowing terms for grades of sand: (i) fine sand will mean amineral-based particle having a mean diameter of between about 0.060 mmand about 0.250 mm; (ii) medium sand will mean a mineral-based particlehaving a mean diameter of between about 0.20 mm and about 0.65 mm; and(iii) coarse sand will mean a mineral-based particle having a meandiameter of between about 0.50 mm and about 1.0 mm (unless specificallyindicated otherwise). (Very coarse sand will mean a mineral-basedparticle having a mean diameter of between about 1.0 mm and about 2.0mm, and gravel will mean a mineral-based particle having a mean diameterof greater than about 2.0 mm.) It will be appreciated that thejust-described grades of sand include some overlap between the upper andlower mean particle diameters between grades. For example, the upper endrange for fine sand (i.e., 0.250 mm) overlaps the lower end range formedium sand (i.e., 0.20 mm) by 0.050 mm, and the upper end range formedium sand (i.e., 0.65 mm) overlaps the lower end range for coarse sand(i.e., 0.50 mm) by 0.15 mm. These overlaps in particle sizes will notconstitute more than about 25% of the total material (between sandgrades), and will not affect the overall process for forming the porousgranular materials, and the unitized formed construction materials, asprovided for herein.

It will be further appreciated that the term sand, as used herein, isused to refer to a mineral-based particle (as described above), and isnot to be constrained in any way by other extrinsic definitions of sand.In particular, the term sand, as used herein, does not mean that thematerial is primarily quartz-based. That is, the term sand, as usedhere, is meant to refer to mineral-based particles having the gradationsdescribed above.

Materials that can be Used in Formulating the Mineral-Based PorousGranular Materials.

Materials that can be used to manufacture the mineral-based porousgranular materials provided for herein include arkose. Arkose is asedimentary rock formed from the remains of other rocks, and morespecifically a type of sandstone containing at least 25% feldspar.(Feldspar is the name given to a group of minerals distinguished by thepresence of alkali, alumina and silica (SiO₂) in their chemistry. Thisgroup includes aluminum silicates of soda, potassium, or lime.) Morespecifically, materials that can be used to manufacture themineral-based granular materials provided for herein include arkosematerial from the Precambrian series of ultrafine clastic nature (i.e.,made up of fragments of preexisting rock), preferably having ahomogeneous nature. Such materials can be obtained from the Burkeformation and the St. Regis formation (both of which can be found inwestern Montana, United States). In a first example the arkose ispreferably about 50% felsic (i.e., minerals including feldspar,feldspathoids, white mica (such as muscovite and sericite) or goldenmica (such as sodic paragonite)), 35% quartz, and 15% volatilecomponents (i.e., components which will sublimate and/or vaporize whensubjected to temperatures in excess of about 950° C.). The volatilecomponents can include low-iron metal sulfides such as, for example,zinc sulfide (ZnS) and low-iron metal disulfides such as molybdenumdisulfide (MoS₂). The felsic component is preferably provided by using amicaceous rock material which provides a precursor to the felsiccomponent when heated (as discussed below), thus generating thedesirable felsic components such as sodic feldspar (e.g., NaAlSi₃O₈,NaAl₂[(OH)₂|AlSi₃O₁₀]) and/or potassic feldspar (e.g., KAlSi₃O₈). (Othermaterials that can be used which provide the desirable felsic componentprecursors include sericitized rhyolites and sericitized granites.) Thismaterial selection is preferable in forming the desired porosity of thegranular particles, and in forming unitized construction materialstherefrom (as described below), for the following reasons:

(1) A low-quartzitic (i.e., less than about 35% quartz) felsic materialallows for a relatively low sintering temperature (of about 1900-2150°F., or about 1040-1180° C.) in order to fuse the particles to oneanother, versus a more quartrzitic-based material (i.e., a materialhaving more than about 35% quartz), which requires a higher temperaturerange (e.g., about 2000-2500° F., or about 1090-1370° C.) in order toachieve sintering.

(2) A sodic and/or potassic felsic material is more resistant tochemical attack (i.e., chemical decomposition) as compared to a felsiccalcium silicate (e.g., CaAl₂Si₂O₈) and/or a felsic magnesium silicate(e.g., MgAl₂Si₂O₆), such as can occur when the material is subjected tocomponents such as ice melters and the like.

(3) The quantity of quartz (i.e., less than about 35%) allows for asolid framework that affords the solid portion of a liquid-solidsintering basis to occur when heated to the desired processingtemperature of between about 1065-1150° C. (about 1950-2100° F.), atwhich temperature the feldspar portion of the material becomes flowable(i.e., liquid and/or plastic).

(4) The volatile component portion of the material, through sublimationand/or vaporization of a portion of the lattice adjacent to the felsicand quartz units of the material, allows for the maintenance of porosityof the particles if the particles are to be later sintered to oneanother (e.g., at a temperature which allows for sintering of theparticles to one another in order to form a unitized building material).

Another material that can be used to manufacture the mineral-basedporous granular materials provided for herein is sericitized igneousrock such as rhyolite (which typically includes more than 69% SiO₂).Rhyolite can also include molybdenum disulfide in rhyolitic porphyrites,such that a mica/feldspar component in the rock is with the molybdenumdisulfide.

In addition to using feldspathic arkose and sericitized igneous rocksuch as rhyolite, the mineral-based porous granular materials providedfor herein can be manufactured using arkosic quartzite, and morepreferably micaceous quartzite or micaceous arkosic felsite. Preferably,the mica within the arkose is muscovite or paragonite. Muscovite is aphyllosilicate mineral including aluminum and potassium with the formulaKAl₂(AlSi₃O₁₀)(F,OH)₂, or (KF)₂(Al₂O₃)(SiO₂)₆(H₂O). Paragonite is a micamineral having the empirical formula NaAl₂[(OH)₂|AlSi₃O₁₀]. Morepreferably the mica component in the arkose has a low iron content(e.g., 3% or less), or no iron, and more than about 4% potassium contentin the case of muscovite, and more than about 4% sodium in the case ofparagonite. In one example, the micaceous arkose had about 6% potassium.Still more preferably, the mica component in the arkose is small-grained(for example, between about 10⁻³ meter and 10⁻⁵ meter in diameter, andpreferably with an average order of magnitude of 10⁻⁴ meter indiameter), and evenly distributed within the arkose. The micaceousarkose should preferably contain more than 20% by weight of mica, andpreferably at least about 40% mica. More preferably the micaceous arkoseshould have a ground mass of between 30% and 70% of the overall startingmaterial. One example of a source for such micaceous arkose is themiddle and lower Burke formation in western Montana, United States. Themica content in the micaceous arkose from the Burke formation has about40-60% mica content. When the micaceous arkose is heated to theprocessing temperature (described more fully below) the reaction ismuscovite+quartz->K-feldspar+aluminum silicate+steam, orparagonite+quartz->sodic feldspar+aluminum silicate+steam. Aluminumsilicate forms as a fibrous material. It is believed that the formationof the aluminum silicate, and the vaporization of the water, result inthe desirable porous properties of the resulting K-feldspar.

In another example the starting material includes at least 70% by weightof a micaceous arkose rock material, and at least about 50% by volume ofthe starting material has a mean diameter of between about 0.060 mm andabout 0.65 mm. In this example kilning of the starting material (at atemperature of between about 1100° C. and about 1300° C.) transforms atleast 40% (by volume) of micaceous components in the micaceous arkoserock material into feldspar which contains metal sulfides, and evolvesat least 30 percent (by volume) of the metal sulfides within thefeldspar from the feldspar as metallic oxides. In this example thestarting material includes between about 10% and 40% by weight ofquartz, and between about 20% and 40% by weight of metallic compoundswhich are reacted to form the metal sulfides. Further in this example,the feldspar is at least about 80% or more (by weight) of a sodicmaterial, a potassic felsic material, or a combination thereof.

In addition to using naturally-occurring materials (as described above),the starting material to manufacture the mineral-based granular porousmaterials of the present disclosure can include manufactured engineeredmineral-based materials which are prepared (e.g., by means such ascrushing and/or grinding) to put them into the desired size (i.e., meandiameter) for further processing. For example, primarily muscovite orsericite rock can be ground to a fine grain size and mixed with groundfine grained quartz.

In one variation the starting materials for the formation of the porousmineral-based granular material preferably contain at least about 5% (byweight), and more preferably at least about 25% (by weight), of avolatile component such that when the starting materials are subjectedto a temperature of between about 950-1200° C. (about 1750-2200° F.),the volatile components of the starting materials will sublime and/orvaporize from the surfaces of the starting materials, thus creating, inaddition to the mica-to-feldspar reaction described below, the desiredporosity. The volatile components exclude components which are liquid ator below about 200° C. (such as liquid water), and are mineralcomponents which are chemically bonded to the surfaces (as well as tothe inner matrix) of the granules of the starting material. Examples ofsuch volatile components include (without limitation), metal sulfides(such as, by way of example, zinc-sulfide, iron sulfide, copper sulfideand molybdenum disulfide). (When the starting materials are manufacturedusing mineral-based materials, the percentage of volatile componentswill typically be lower, such as about 20% or less, by weight.) Further,subjecting the starting materials to this temperature range (i.e.,between about 950° and 1200° C.) may cause some of the startingmaterials to sinter to one another, although this is not a requirementfor the process. In the event that sintering of the starting materialsdoes occur (due to the composition of the starting materials), then theresulting product can be crushed (if desired) in order to achieve thedesired sand (or gravel) grade for post-processing or use of theresultant product (porous mineral-based granular material). Thisphenomenon of evolving metal sulfides in order to create porosity on(and within) the grains of the starting materials is more prevalent whenthe starting materials contain a high percentage of feldspar and/ormica. When the starting materials contain a high percentage of micaceousmaterial, then the process can include generating porosity by conversion(under heat during the kilning process) of the micaceous components tofelsic components, and then subsequent evolution of metal sulfides inthese felsic components into evolved volatile components. The startingmaterials can be derived from primarily micaceous arkosic rock, fromprimarily felsic arkosic rock, from a rock containing at least somemicaceous content, from a rock containing at least some feldsparcontent, and from combinations thereof.

The process (method) for manufacturing the porous mineral-based granularmaterials provided for herein is generally performed as follows: (i) astarting material (as described above) is provided as a loose (i.e.,non-consolidated) granular material, preferably of a fine to medium sandgrade (as described above); (ii) the starting material is placed as abed within a kiln; (ii) the kiln is heated to a temperature selected toevolve micaceous components into feldspathic components, and/or toevolve volatile mineral components from the granular starting materials;(iii) the starting material is maintained in the heated kiln for aperiod of time selected to evolve about 50% or more of the micaceouscomponents and/or the volatile mineral materials from the granularstarting materials; and (iv) the processed starting materials are thenremoved from the kiln. The materials removed from the kiln can then beused directly, or post-processed, as described more fully below. Theprocess (for manufacturing the porous mineral-based granular materialsprovided for herein) is preferably performed as a batch process,although it can also be performed as a continuous process by placing thestarting materials on a conveyor which moves through the kiln.

Bed Thickness of Starting Materials.

The thickness (i.e., depth) of the bed of starting materials is selectedto preferably achieved evolution (i.e., sublimation and/or vaporization)of at least about 50% of the volatile mineral components located on thesurfaces, and/or in the lattice of minerals such as mica and feldspar,of the granular starting materials, without causing an undesirabledegree of fusing (i.e., sintering) of the starting material granules toone another, and while also providing for efficiency of materialthroughput. That is, a thin bed (e.g., a 1 inch (2.5 cm) deep bed) ofstarting material can be used, but while this thin bed thickness hasbeen found to achieve the desired results (in the way of evolving thevolatile mineral components located on the surfaces of the granularstarting materials), it reduces the volume of material that can besuccessfully processed over time. On the other hand, a thick bed (e.g.,a 5 inch deep bed) of starting material can be used, but while this bedthickness has been found to achieve the desired results (in the way ofevolving the volatile mineral components located on the surfaces of thegranular starting materials), it requires additional time, and furtherresults in an undesirable degree of fusion (sintering) of the startingmaterials at the outer surfaces (upper and lower surfaces) of the bed. Ihave determined that, for the starting materials described above, astarting material bed thickness of less than about 3 inches (andpreferably about 2.25-2.75 inches—i.e., about 5.7-7 cm) achieved adesired degree of evolution of the volatile mineral components locatedon the surfaces, and/or within the mineral lattices, of the granularstarting materials (in order to achieve the desired degree of porosityfor the resultant product of a mineral-based porous granular material),while also providing for a desirable processing time and avoiding anunacceptable level of sintering of the starting materials. Further, thedesired bed thickness of the starting materials can vary based on thestarting materials. To this end, a preferred starting-material bedthickness (bed depth) can be determined by performing bed thicknesstrial tests, using different bed thicknesses (for the same startingmaterial) and then analyzing the resulting product for (primarily)porosity. (Such can be determined by examining samples of the resultantproduct under a microscope, including a electron-scanning microscope, todetermine the degree of surface porosity achieved by using the selectedbed depth, temperature range (as described below), and processing time(also as described below).)

Processing Temperature and Temperature Regimen.

Preferably, when the bed of starting materials is placed into the kiln,the kiln is at an initial temperature of less than about 260° C. (about500° F.) in order to allow components (such as water) to evolve from thestarting materials, thus reducing the likelihood of subsequent chemicalreactions between the evolving mineral volatile elements and watervapor. For example, prior to increasing the kiln from the startingtemperature to the basic processing temperature, the kiln can held atthe starting temperature for a period of between about 20 minutes and 30minutes per centimeter of bed thickness. This initial temperature ispreferably maintained for a period of about 20 minutes per centimeter ofdepth of the bed of starting material. Afterwards the kiln temperaturecan be increased to the range of the basic processing temperature, whichcan be defined by a maximum desired temperature. The basic processingtemperature is a temperature range selected to achieve evolution one ormore of: (i) evolution (via chemical transformation) of at least about50% of the micaceous components into felsic components; and/or (ii)evolution (via sublimation and/or vaporization) of at least about 50% ofthe volatile mineral components in the granular starting materials.Further, the temperature range is selected to avoid an undesirabledegree of fusing (i.e., sintering) of the starting material granules toone another. In general, a basic processing temperature range of betweenabout 950° and 1200° C. (about 1750-2200° F.), and more preferably, abasic processing temperature range of between about 1100° and 1200° C.(about 2000-2200° F.), has been determined to achieve the desiredresults for selected felsic arkose-based starting materials, and betweenabout 950° and 1000° C. (about 1750-2000° F.) for selected micaceousarkose-based starting materials, although this temperature range canvary based on the starting materials and other variables. (The basicprocessing temperature is the mean temperature at which the startingmaterials are held for a selected time in order to achieve the desiredlevel of evolution of the volatile mineral components from the surfacesof the starting materials.) Further, the desired basic processingtemperature is primarily based on the starting materials—i.e., thetemperature that will result in the desired level of evolution of thevolatile mineral components from the surfaces, and/or within thelattices, of the selected starting materials. The time period forincreasing the kiln temperature between the starting temperature [e.g.,about 250° C.] and the desired basic processing temperature [e.g., about950° C.] can be about 15 minutes per inch of starting-material beddepth. For example, for a bed depth of starting material of about 3inches, the temperature can be increased from a starting temperature ofabout 250° C. to a basic processing temperature of about 950° C. over aperiod of time of about 30 minutes (i.e., about a 700° C. temperatureincrease over 30 minutes, or a kiln temperature increase from thestarting temperature to the desired basic processing temperature ofabout 23° C. per minute). This rate of kiln temperature increase can beheld as a constant (regardless of the depth of the starting material),or can be increased (or decreased) as a function of starting materialbed depth. (E.g., for a starting material bed depth of about 1 inch, thekiln-ramp-up temperature can be about 100° C. per minute, i.e., aboutthree times the rate for a starting material bed depth of about 3inches.)

Processing Time.

The starting materials are preferably held at the desired basicprocessing temperature (typically, the maximum processing temperature)for a period of time (that is, the basic processing temperatureprocessing time) which preferably evolves at least about 50% of thevolatile mineral components located on the surfaces, and/or within thelattices, of the granular starting materials from the startingmaterials. The basic processing temperature processing time does notinclude time required to achieve the basic processing temperature withinthe kiln, but is rather the time that the starting materials are heldwithin the kiln at or about the basic processing temperature. Preferablythe basic processing temperature processing time is maintained forbetween about 15 minutes and 45 minutes for each centimeter of bedthickness of the starting materials. In one example, the basicprocessing temperature processing time is about 1 hour per inch (about2.5 cm) of bed depth (i.e., thickness) of starting material.

EXAMPLE

In one example, a starting material was prepared from an essentiallymicaceous arkosic rock which was initially prepared (i.e., crushedand/or ground) to a mean diameter of about 0.25 mm (with about 20% orless of the starting material being greater than about 0.30 mm indiameter, and about 20% or less of the starting material being less thanabout 0.20 mm in diameter). In this example, at least about 60% of thestarting material had a mean particle diameter of between about 0.20 mmand 0.3 mm. The starting material was formed on a bed having a thickness(i.e., depth) of about 3 inches (about 7.6 cm), and was placed in a kilnat an initial temperature of about 200° C. The kiln was then heated to atemperature of about 1200° C. over a period of time of about 1.5 hours,and then held at a basic processing temperature of between about1150-1225° C. (about 2100-2250° F.), for a period of time of about 3(three) hours. Afterwards the kilned starting materials were cooledwithin the kiln to ambient temperature (without any temperature controlover the cooling). It will be appreciated that the kilned startingmaterials can be cooled at controlled rates (e.g., slower or quickerrates than are achieved by subjecting the kilned materials to ambienttemperature), and the cooling can be performed in a separate coolingchamber. For example, the kilned materials can be quenched by subjectingthem to a rapid cooling regimen, or they can be annealed by subjectingthem to a slower cooling regimen. Quenching can also be used tofacilitate fracturing of any sintered materials, thus making it easierto crush any sintered material to a desired size.

Processing Variables.

As indicated above, the methods provided for herein for manufacturing amineral-based porous granular material include the following processvariables: (i) starting materials; (ii) bed thickness (i.e., bed depth)of the starting materials when introduced to the kiln; (iii) initial anddesired basic processing temperature of the starting materials withinthe kiln; (iv) temperature ramp-up rate within the kiln from the initialtemperature to the desired basic processing temperature; (v) the desiredbasic processing temperature; (vi) the time to hold the startingmaterials at the desired basic processing temperature within the kiln;and (vii) a cooling process of the product from the kiln. The objectiveis to produce a mineral-based granular material having a high porosity,but with small pore size. To this end, I have determined that this canbe accomplished by the following process: (i) providing a startingmaterial comprising an arkose rock based material, a manufacturedmineral-based material, or a combination thereof; (ii) processing thestarting material (or materials) by crushing, grinding, or othermechanical means to achieve a desired selection of particle sizes of thestarting material(s) for subsequent processing; (iii) optionally,separating the desired selection of particle sizes of the startingmaterial(s) by sorting, screening and/or other means to obtain apreferred selection of starting material particle sizes; (iv) optionallywashing the preferred selection of starting material particles to removefines and the like which can be adhered to surfaces thereof by staticelectrical forces and the like; (v) placing the preferred selection ofstarting material particles into a bed on a support surface; (vi)placing the bed of the preferred selection of starting materialparticles into a kiln (the kiln having a preferred starting temperatureof less than about 200° C.); (vii) increasing the temperature of thekiln to a basic processing temperature of between about 1150-1225° C.for a basic processing temperature processing time selected to evolve atleast about 50% of volatile mineral components located on the surfacesof the preferred selection of starting material particles from thepreferred selection of starting material particles; (vii) cooling thekilned preferred selection of starting material particles to an ambienttemperature; (viii) any post-processing (e.g., crushing or grinding ofany sintered materials) to achieve a desired end-size; and (ix)optionally repeating the process of crushing and kilning the startingmaterial.

FIG. 1 provides a flowchart 100 depicting an exemplary method formanufacturing a porous mineral-based granular material according to atleast one method provided for herein. (It will be appreciated that theflowchart of FIG. 1 depicts only one example of a method formanufacturing a porous mineral-based granular material according to themethods provided for herein, and that the method depicted in FIG. 1 caninclude fewer steps than are indicated, as well as additional steps notshown.) In the exemplary method depicted in the flowchart 100 of FIG. 1for manufacturing a porous mineral-based granular material, the processbegins at step 102 by providing a micaceous-arkose rock material as astarting material. (As described above, the method can also includeproviding a manufactured mineral-based material, an arkose rock, asericitized rhyolite, or a sericitized granite as all or part of thestarting material. While combinations of these various startingmaterials can be used, preferably a single type of starting material isused due to the potential different heating temperatures required toform the desired porosity. For purposes of the example depicted in FIG.1, the starting material is assumed to be a micaceous-arkose rockmaterial.) At step 104 the micaceous-arkose rock starting material isprocessed (by one or both of grinding and crushing) to achieve a meandiameter of about 0.1 mm to about 0.6 mm. (Other size ranges can also beused.) As will be appreciated, the process of crushing and/or grindingthe starting material to achieve the desired mean particle diameter willresult in the production of ancillary fines material within theprocessed arkose rock material. Accordingly, at step 106 the processedmicaceous-arkose rock material (from step 104) can be washed and/orleached to remove the fines. At step 108 the cleaned processedmicaceous-arkose rock material (from steps 104 and 106) is placed into abed on a support surface. The support surface can be a solid sheet (suchas a sheet of steel) or a screen having a screen size selected toprevent passage of particles of the cleaned processed micaceous-arkoserock material from passing through the screen. At step 110 the supportsurface (now supporting the bed of cleaned processed micaceous-arkoserock material) is placed into a kiln. Then at step 112 the temperaturewithin the kiln is increased to a basic processing temperature ofbetween about 950° C. and about 1250° C., to subject the bed of cleanedprocessed micaceous-arkose rock material to the basic processingtemperature. At step 114 the basic processing temperature within thekiln is held for a basic processing temperature processing time ofbetween about 15 minutes and about 30 minutes for each centimeter of bedthickness of the cleaned processed micaceous-arkose rock material.Holding the kiln at the basic processing temperature for the basicprocessing temperature processing time allows the micaceous componentsto become felsic components, which can then remove metal sulfides fromthe starting material, and also generate water vapor. The metal sulfidesand water vapor are evolved from the starting material throughsublimation, vaporization, or combinations thereof, thus creatingporosity within the kilned starting material (both surface porosity andinterior matrix porosity). Preferably, the kiln is held at the basicprocessing temperature for the basic processing temperature processingtime to allow at least 30% of the metal sulfides which are present inthe micaceous-arkose rock starting material (both on the surfaces, andin the near-surface lattices, of the cleaned processed micaceous-arkoserock material) to evolve into a gaseous form. Thereafter, at step 116,the kilned bed of the cleaned processed arkose rock material is cooledto ambient temperature for subsequent use and/or subsequent processing.

Post-Processing Methods.

After the starting material (as described above) has been initiallykilned (as also described above), the resulting initial mineral-basedkilned material can be further processed, as will now be described. (Itwill be appreciated that the resulting initial mineral-based kilnedmaterial can be used in its own right, without any additionalpost-processing.) The initial mineral-based kilned material willtypically include at least a portion of the granular starting materialsthat have become sintered to one another. For certain uses it isdesirable to crush and/or grind the initial mineral-based kilnedmaterial into a particle size that can be used for an intendedapplication (such as, for example, a fill material, or as a material tobe used in the manufacture of a unitized formed construction material,as provided for herein below). Accordingly, if the initial mineral-basedkilned material is to be used as a fill material (e.g., a materialprovided for the intended purpose of retaining water or the like, or amaterial provided below as a primary porous covering surface foressentially the same purpose), then the initial mineral-based kilnedmaterial can be crushed and/or ground to the size particularly suitablefor the intended use.

Further, the initial mineral-based kilned porous material can be furtherprocessed in order to further increase the porosity of the material.Specifically, the initial mineral-based kilned porous material can becrushed (preferably, to a fine to medium sand grain size), and re-kilnedaccording to the procedures set forth above for the initial kilning ofthe starting materials. The process of crushing the initialmineral-based kilned porous material will expose surfaces of the initialstarting materials that were not exposed in the initial kilning, andwill thus allow additional volatile mineral components within thestarting materials to evolve (i.e., sublime and/or vaporize), thusfurther increasing the porosity of the starting materials. This processof crushing the kilned starting materials and re-kilning the crushedproduct (in order to increase porosity of the starting materials byfurther evolution of volatile mineral compounds therefrom) can berepeated again and again. (When the sintered granular particles arebroken apart, new surfaces are exposed which typically include volatilemineral compounds, such as metal sulfides and/or micaceous minerals,that were not reacted, sublimed and/or vaporized previously. By placingthe crushed processed material back into the kiln additional porositycan be achieved. It will be appreciated that the level of porositydesired, and to be achieved by this method of re-kilning already kilnedstarting material, is to be balanced against the cost of crushing andre-kilning the previously processed starting materials.)

Examples of Uses for Porous Granular Materials.

The present disclosure also provides for mineral-based porous granularmaterial manufactured according to the methods provided for herein. Themineral-based porous granular material provided for herein can be usedas an aggregate material for a unitized formed mineral-basedconstruction material, as described more fully herein below. Themineral-based porous granular material provided for herein above canalso be used as a fill material (e.g., beneath the unitized formedmineral-based construction materials described more fully herein below),and can also be used as a filter material to remove solids and othercomponents from liquids or gasses (such as air) passing through a bed ofthe mineral-based porous granular material. By proper selection of thestarting materials, the mineral-based porous granular material can alsobe used as either a fixed or a fluidized bed catalyst.

Use of Porous Granular Materials as a Proppant in Hydraulic FracturingProcesses.

The mineral-based porous granular material provided for herein can bealso used as a proppant in conjunction with a hydraulic fracturingmethod. Hydraulic fracturing of subterranean reservoirs and formationsis performed by injecting a hydraulic liquid into a subterraneanformation via a wellbore. Fracturing of the formation enhances theproduction of desirable fluids (such as oil and gas) thereform. Theinjection of the hydraulic fracturing liquid is oftentimes accompaniedby the inclusion of a proppant in order to hold open the fissures whichresult from the hydraulic fracturing. The use of a mineral-based porousgranular material (as provided for herein) as a proppant is advantageousfrom two standpoints. First of all, the mineral-based porous granularmaterial (when used as a proppant) increases the fluid flow (fluidtransmissivity) of secondary enhanced oil recovery liquids (such as asurfactant and/or an acid) into the fractured reservoir. Second, themineral-based porous granular material (when used as a proppant)increases the fluid flow of recovered liquids from the fracturedreservoir. Both of these desirable attributes result from the surfaceporosity of the mineral-based porous granular materials provided forherein. Accordingly, the present disclosure provides for a method ofimproving enhanced oil recovery by using the mineral-based porousgranular material provided for herein as a proppant in a hydraulicfracturing process of fluid-containing subterranean formations.

Use of Porous Granular Materials as a Soil Supplement.

The mineral-based porous granular material provided for herein can bealso used as a soil supplement. Specifically, I have discovered thatporous granular materials manufactured according to the above disclosuretend to extract moisture from air and conduct the extracted moistureinto soil containing the porous granular materials. This is typicallyachieved during nighttime cooling of air when the dew point allowsmoisture in the air to adhere to particles (i.e. the porous granularmaterials) as a result of an imbalance in water saturation between theair and the porous granular materials. Because the porous granularmaterials will conduct absorbed water molecules into the soil containingthe porous granular materials, the air immediately above the uppersurface of the soil experiences a lowering of humidity, and in order tomaintain equilibrium of humidity within the air, moisture moves from theregions of higher humidity to the areas of lower humidity immediatelyabove the soil. The ability of the porous granular materials to extracthumidity from the air, and to transport the extracted humidity intolower levels of the soil, results in a humidity transfer engine which ispowered by pore water pressure generated by the high hydraulicconductivity of the porous granular material. Accordingly, the presentdisclosure provides for a method of improving the ability of soil toextract moisture from the ambient environment by introducing porousgranular materials of the present disclosure into an upper layer ofexisting soil, and particularly to a depth selected to provide moistureto roots of a crop planted within the soil. As such, the uptake ofmoisture by roots during daytime affords more pore water pressuredifferential during nighttime. In addition to using kilned porousgranular materials as a soil supplement, naturally occurring porousgranular material can also be used as a soil supplement to enhanceextraction of moisture from the air. The porous granular materials cancomprises between about 15% and 40% (by volume) of the upper 30 to 40 cmof topsoil.

Second Embodiment: Unitized Formed Mineral-Based Construction Materials

A second embodiment provides for a method for manufacturing unitizedmineral-based construction materials. By unitized construction materialsI mean construction materials that are provided as discrete constructioncomponents, rather than as a continuous in-situ construction component.An example of a continuous in-situ construction components is, forexample, a poured concrete slab, an applied hot paving material,unconsolidated land fill material (such as gravel), etc. Non-limitingexamples of unitized construction materials include block materials(such as pavers, bricks, prefabricated slabs, etc.), as well asengineered components such as beams, posts and architectural components.The unitized construction materials provided for herein are preferablyfirst formed by placing the starting materials into a mold or the liketo form a unitized element, and the unitized elements are then processed(as described below) to create a unitized construction material asprovided for herein. The process of forming the unitized constructionmaterials generally includes curing cement within the starting materialsto achieve a solid unit, and then heating the solid unit in a kiln toachieve high-strength, and preferably porosity (and permeability), ofthe unitized elements. The process further uses less cement than priormethods for forming unitized construction materials, and in the case ofunitized construction materials requires substantially less energy inputfor kilning than prior art clay-based materials. An additional advantageof the current disclosed methods of manufacturing unitized constructionmaterials over the prior art is a significant reduction in the timerequired to heat the formed unitized construction materials. Prior artheating regimens for unitized construction materials made primarily fromclay typically last between about 24 and 48 hours (includingpreheating), whereas a heating regimen for a similar sized unitaccording to the current disclosure is around 6 hours. This not onlyincreases the rate at which the unitized construction materials can beproduced, but also significantly reduces the energy required tomanufacture the units.

Starting materials for the unitized construction materials provided forherein include an aggregate, a cementing agent, and water. As describedbelow, in certain variations a sublimation agent can also be used. Eachof the starting materials will now be described in more detail.

The aggregate for the unitized construction materials can include anymineral-based granular material. Preferably the aggregate is provided asa sand particle, and more preferably as a felsic sand, a micaceous sand,a sericitized igneous sand, or a combination thereof. Such felsic,micaceous and sericitized igneous sands can be provided as components ofan arkose rock or a rhyolitic or sericitized metamorphic rock, asdescribed above with respect to the methods for manufacturing porousmineral-based granular materials. However, in certain instances theaggregate can be gravel and/or crushed rock. Combinations of sand,gravel and/or crushed rock can also be used as the aggregate. In certaininstances it can be desirable to use porous mineral-based sand, such ascan be manufactured by the processes described hereinabove. Theaggregate material will typically comprise about 70-80% (by weight) ormore of the total starting materials, and preferably between about85-95% by weight of the finished material. The aggregate preferably hasan average mean diameter of less than about 5 mm, and more preferably anaverage mean diameter of about 1.0 mm or less. When the aggregate isused to form small unitized construction materials (such as pavers,roofing tiles, flooring tiles and the like), it is desirable that thefinished unitized construction materials have a smooth finish along thesurfaces and edges, in which case the average mean diameter for at least50% or more of aggregate is between at least about 0.3 mm and at leastabout 0.6 mm, and more preferably a mean diameter of about 0.5 mm orless.

The cementing agent is used primarily to hold the aggregate into aunitized shape once the mixture of aggregate and cementing agent havebeen removed from any form used to shape the unitized constructionmaterial. Preferably, the cementing agent is a hydraulic cement, such asPortland cement. The amount of cementing agent used is preferablybetween about 2.5% and 10% (by weight) of the total starting materials.The water of the starting materials is used to initiate and furtherfacilitate the curing process (i.e., the hydration process) of thecementing agent in order to bind the cementing agent primarily to theaggregate (and, to a much lesser degree, to any sublimation agent). Theamount of water to be added to the cementing agent is preferably betweenabout 20-40% (by weight) of the cementing agent, and is selected toachieve an essentially complete hydration reaction of the cementingagent with the water. The amount of water to be added to the cementingagent can be as high as about 70% (by weight) of the cementing agent. Inaddition to adding water to accomplish the hydration reaction in thecement, it is also important that the overall mixture of startingmaterials have sufficient water to wet the surfaces of the aggregate.Depending on the moisture state of the aggregate at the time of mixing,additional water (in the amount of around 2-3 times the quantityrequired for the hydration reaction) may need to be added to the mixtureof the starting materials. The amount of additional water to be added towet the aggregate can be determine by performing a slump test, and/orusing a moisture meter. It will also be appreciated that removing finesfrom the aggregate prior to mixing (such as by washing or the like) canreduce the quantity of additional water to be added to the mixture. Thecementing agent can also include lime mortar and fly ash. Fly ash (i.e.,residues generated by coal combustion) includes substantial amounts ofsilicon dioxide (SiO₂) (both amorphous and crystalline), aluminum oxide(Al₂O₃) and calcium oxide (CaO). Fly ash typically also includes traceamounts (the quantity depending upon the source of the coal used togenerate the fly ash) of molybdenum and vanadium, both of which can actas sublimation agents, as well as other metal sulfides which can assistin removing calcium from the cured cement once the constituentcomponents are later kilned. The presence of silicon dioxide within thecementing agent also facilitates sintering of components within thestarting materials during kilning. In one example the cementing agentcan include about 50% (by weight) of fly ash.

As indicated above, the starting materials can further include asublimation agent, which is used primarily as a sacrificial agent whichsublimes during kiln heating of the cured aggregate/cement startingmaterials. Suitable sublimation agents can also act to facilitategranules of the aggregate to move into closer proximity and contact withone another. That is, the sublimation agent does not necessarily need tosublime during the kilning process, but can act as an assistantcomponent in facilitating the sublimation of other components from thestarting materials during the kilning process. (In the followingdisclosure, comments regarding the sublimation agent as actuallysubliming should be understood as being limited to those examples wherethe sublimation agent itself sublimes, but are not considered to limitthe sublimation agent as being required itself to sublime, and thusallow for the sublimation agent to aid in the sublimation of othercomponents while not specifically itself subliming.) When thesublimation agent includes a component (such as molybdenum) which isintended to sublime, then the sublimation temperature is preferably lessthan the calcination temperature for calcium components in the curedcement (e.g., about 450-700° C. (i.e., about 850-1300° F.) formolybdenum disulfide), which is selected to be below the expectedsintering temperature of the aggregate (e.g., about 1000-1300° C.(approx. 1800-2300° F.). However, when the sublimation agent is areaction component such as copper sulfate, then the temperature to whichthe mixture is to be heated is a temperature at which the copper sulfate(or other selected copper compound) will react with calcium componentsin the cured (hydrated) cement in order to form compounds such ascalcium copper silicates, thus alternating and/or removing reactivecalcium oxides from the cured cement. The sublimation agent can have asublimation temperature of up to about 1200° C., and particularly whenthe aggregate material includes a minor percentage of clay (whichincreases the sintering temperature of the aggregate). In this way thelikelihood of fracturing sintered aggregate (during the kilning processof the formed unitized construction materials) is reduced. Thesublimation agent is preferably a metal sulfide that will not chemicallyreact with the cementing agent during the curing (i.e., hydration) phaseof the cementing agent with the aggregate, and/or does not appreciablyreduce the ability of the cementing agent to cure to strength in atimely manner. One example of a sublimation agent that can be used inthe process is molybdenum disulfide (MoS₂). Other examples of asublimation agent that can be used include tungsten disulfide (WS₂),vanadium disulfide (VS₂), copper compounds (described more fully below),and zinc compounds. These and some other metal sulfides can sublime fromthe aggregate and/or the cement, and/or aid in the sublimation of othercomponents from the starting materials. As described further below,during kilning of the starting materials (in order to form the unitizedconstruction materials) a significant quantity (perhaps as much as 70%)of the sublimation agent is evolved (e.g., via sublimation) from themixture of starting materials in a gaseous form, and/or is chemicallyreacted with other components to facilitate the sublimation thereof fromthe starting materials. Any evolved sublimation agent can be recoveredand (after processing) reused. The amount of sublimation agent to beused can be between about 5-70% (by weight) of the cementing agent, andpreferably between about 10-50% (by weight) of the cementing agent. Anadditional advantage to using a lubricant such as molybdenum disulfideas the sublimation agent is that molybdenum disulfide acts as a frictionreducer between the grains (granules, or particles) of the aggregate, aswell as the cementing agent, thus increasing packing of theaggregate/cement, and also improving workability of the mixture ofstarting materials (as described further herein). The sublimation agentcan be an additive to the starting materials, a constituent component ofthe starting materials (e.g., the aggregate and/or the cementing agent),or a combination thereof.

As an alternative to molybdenum disulfide as a sublimation agent is theuse of anhydrous copper sulfate (also known as copper (II) sulfate,cupric sulfate, and generically copper sulfate, having the chemicalformula CuSO₄, which is to be distinguished from copper (I) sulfate (orcuprous sulfate), having the chemical formula Cu₂SO₄). In this instancethe copper sulfate (CuSO₄) does not sublime directly from the startingmaterials, but rather acts as an agent to extract metallic componentsfrom the micaceous components of the aggregate, and metallic componentsfrom the cement, which then combine with calcium components from thecured cement, and the combined extracted metallic components and calciumcomponents are then sublimed from the cured and kilned mixture ofstarting materials. A particular advantage to the use of anhydrouscopper sulfate over molybdenum disulfide as a sublimation agent is thatanhydrous copper sulfate is historically available at a much lower costthan is molybdenum disulfide. Further, an additional advantage to theuse of anhydrous copper sulfate over molybdenum disulfide as asublimation agent is that anhydrous copper sulfate appears to provideenhanced properties of permeability (e.g., water conductivity) in thefinished product (as indicated in the example herebelow). In addition tocopper sulfate (CuSO₄) and other copper-sulfur compounds (such asCu₂SO₄), other non-sulfur copper compounds can be used as thesublimation-reaction agent, including copper oxide (CuO), coppercarbonates (e.g., CuCO₃, Cu₂CO3), copper acetate (Cu(OAc)₂, where OAc—is acetate (CH₃CO₂—).), and copper hydroxide (Cu(OH)₂). These non-sulfurcopper compounds can be used when the cementing agent and/or theaggregate has sufficient sulfur available to bind with the copper fromthe copper compound. The copper compound used as thesublimation-reaction agent is preferably selected to avoid the formationof copper oxide in the finished product (which can reduce strength inthe end formed unit). Further, copper compounds such as copper halides(e.g., copper chloride) are not desirable as the sublimation-reactionagent. The selection of the copper compound used as thesublimation-reaction agent is selected to tie copper to calcium (fromthe hydrated cement), and also to ensure that sufficient sulfur isavailable to combine with freed metal components from the cement and theaggregate to form metal sulfides which can sublimate from the mixture ofstarting materials.

When the aggregate has a high surface porosity (such as the porousmineral-based sand described above), then a larger quantity of asublimation agent such as molybdenum is needed (e.g., about 40-70% (byweight) of the cementing agent) since the sublimation agent will tend tobe drawn into the surface pores of the aggregate. Further, a previouslykilned and crushed clay (such as fine crushed tile material) can beadded to the sublimation agent. As the sublimation agent is reduced fromthe starting materials during kilning, the fine crushed clay will beginto sinter to the aggregate at a temperature starting at about 650° C.(about 1200° F.).

The sublimation agent can also be provided in a paste (or emulsified)form, versus being provided in a powdered form. For example, molybdenumdisulfide (MoS₂) can be provided in a paste, and mixed in with the otherstarting materials using a mixer (as described below). Additionally, anemulsified (or paste) form of molybdenum disulfide can be pre-mixed witha clay material, which can aid in forming inter-granular porosity (i.e.,pores between the granules of the aggregate) as also described morefully below. Further, calcium molybdate (CaMoO₄) can be added to thestarting materials as a part of the sublimation agent, but preferablyrequires additional kilning time to evolve the undesirable calciumcomponent thereof (which can present a reactive component, and thusreduce the chemical resistance of the end unitized construction materialproduct).

In certain instances, when the unitized construction material to beformed is relatively thin in a minimum dimension (e.g., about 1.5 inches(about 40 mm)), and the sublimation agent to be used is copper sulfate(or another copper compound), then the formed unitized constructionmaterial (following curing, but prior to kilning), can be immersed in aliquid solution of the copper-based sublimation agent (versus mixing thecopper-based sublimation agent in with the starting materials).

The starting materials for the unitized construction materials providedfor herein can further include a pre-kilning binding material which aidsin solidifying the starting materials prior to kilning (and thusfacilitates handling of the formed and cured starting materials). Thususe of a pre-kilning binding material can also reduce the quantity ofcementing agent that is required to hold the cured starting materialsinto a solidified form. (By reducing the quantity of cementing agent inthe starting materials, additional direct sublimation of the sublimationagent, and thus increased porosity of the finished product, can beachieved, as described more fully below.) An example of a pre-kilningbinding material which can be used in the processes described hereininclude glass fibers and mineral fibers. An additional advantage tousing a pre-kilning binding material (such as a glass fiber) is that atthe sintering temperature for the starting materials (described morefully below), the pre-kilning binding material can sinter with theaggregate.

As indicated above, when micas (such as muscovite) are subjected tokilning temperatures in excess of 900° C., they are found to developdesirable micoporosity. Rather than using a micaceous sand as a startingmaterial aggregate (or in addition to, in order to provide the desiredamount and size of the mica particles), the aggregate can besupplemented with ground mica particles and mixed with quartz particlesin order to achieve the desired reaction ofmuscovite+quartz->K-feldspar+aluminum silicate+steam (orparagonite+quartz->Na-feldspar+aluminum silicate+steam). In thisinstance the mica particles should be of a size and distribution withinthe mixture to achieve contact between a large percentage of the micaparticles and the quartz particles. Likewise, the starting materials canbe supplemented with ground quartz in order to achieve a desired ratioof mica particles to quartz particles (i.e., a ratio of about 1:1),which provides for generally evenly distributed sintering of resultingfeldspathic particles to quartzitic particles.

The starting materials for the unitized construction materials providedfor herein can also include one or more reinforcing elements, such assteel reinforcing bars and/or reinforcing fibers, which can be embeddedwithin the mixture of starting materials prior to kilning thereof. Theuse of such reinforcing elements is describe more fully below.

The starting materials for the unitized construction materials providedfor herein can also include one or more coloring agents. A coloringagent can include a dye. A coloring agent can also include a chemicalcompound which reacts with one or more of the other starting materialsat (or below) the processing temperature (described below) in order toproduce a chemical component in the resulting unitized constructionmaterial having a specific hue. Coloring agents can also includecompounds such as iron chromate and manganese chromate which arecompatible with (i.e., do not degrade) the sintering temperature for thestarting materials.

Preparation of Starting Materials for Unitized Construction Materials.

In order to manufacture the unitized construction materials provided forherein, the starting materials are first prepared, then mixed, thenformed, then cured, and then kilned, to finally produce the unitizedconstruction materials. The preparation of the starting materials beginsby selecting and providing the desired grade of the aggregate (i.e., theparticle type, particle size, and particle porosity, or combinationsthereof) to be used in the unitized construction materials. The processof providing the starting material aggregate can include screening of abase aggregate material (to achieve desired particles sizes), washing ofa base aggregate material (to remove fines), processing of a baseaggregate material (for example, kilning, as described above), andmixing of different grades of base aggregate materials (i.e., mixing ofdifferent base aggregate materials, or different mineral-basedgranules). The processing (if any) of the base aggregate material (ormaterials) results in the starting material aggregate (i.e., theaggregate material that will be used in the manufacture of the unitizedconstruction materials). The preparation of the starting materialsfurther includes providing the cementing agent (preferably, in a finepowdered form), and providing the sublimation agent (if any) either in apowdered form or a paste form. The preparation of the starting materialscan further include leaching the base aggregate material in order toremove soluble materials that can later degrade in the finished product.An objective in mixing the starting materials is to obtain adjacency(and contact) of reactants (e.g., cementing agent, aggregate, and anysublimation agent, being in contact with one another in variouscombinations, and/or being separated by water). When the sublimationagent is a soluble compound (such as copper sulfate), then thisadjacency is enhanced since the liquid solution (containing copper) willhave increased contact with cementing agents and aggregate components ascompared to non-soluble sublimation agents (such as molybdenumdisulfide).

Mixing of the Starting Materials.

The mixing of the starting materials (i.e., the aggregate, the cementingagent, any sublimation agent and the water) for the unitizedconstruction materials can be performed in any number of ways. However,the objective is to achieve a homogeneous mixture of the startingmaterials such that the starting materials are relatively evenlydistributed throughout the mixture. A preferred method of mixing thestarting materials for the unitized construction materials is to firstmix a powdered form of the cementing agent and a powdered form of anysublimation agent (sublimating agent) using a mixer. The powderedsublimation agent can be slowly added to the powdered cementing agent asthe two components are mixed using the mixer. The desired mixing timefor mixing of the powdered cementing agent and the powdered sublimationagent can be determined by sampling the mixture at selected timeintervals (e.g., every 10 minutes), and then viewing the mixture under amicroscope to determine if the desired level of mixing has beenaccomplished. For example, if the mixture of powdered cementing agentand powdered sublimation agent is to be about 80% (by weight) ofcementing agent and about 20% (by weight) of sublimation agent, then themixture of cementing agent particles and sublimation agent particlesshould be such that any sample of the mixture should desirably includeabout 83 percent of cement particles and about 17 percent of sublimationagent particles. (For example, molybdenum disulfide, a potentialsublimation agent, has a molecular weight of about 160 grams per mole,whereas Portland cement, a potential cementing agent, has an averagemolecular weight of about 65 grams per mole. Accordingly, in order toachieve a mixture of about 80% (by weight) of cementing agent and about20% (by weight) of sublimation agent, then the mixture will need to havea ratio of about 8 or more cementing particles for every sublimationparticle in order to achieve a stoichiometric proportion for thechemical between the cured cement and the sublimation agent.)

In the preferred method for mixing of the starting materials for theunitized construction materials, once an acceptable distribution ofcementing agent materials and sublimation agent materials has beenachieved (as described above), then the mixture of the cementing agentmaterials and sublimation agent materials can be mixed with the startingmaterial aggregate. (If the starting material aggregate is composed oftwo or more base aggregate materials, e.g., sand and gravel, the baseaggregate materials can be first mixed into a generally homogeneousmixture into the starting material aggregate.) Once the startingmaterial aggregate and the cementing-agent/sublimation-agent mixtureshave been combined (by mixing) to achieve a relatively homogeneousdistribution of the indicated starting material components (as can bedetermined by microscopic examination of the mixture), then the watercan be added to the aggregate/cementing-agent/sublimation-agent mixture.The water is preferably added at a rate (or mixed in over a mixing time)to ensure a generally homogeneous mixture of the aggregate, cementingagent, sublimation agent, and water. The preferred mixing time for thefinal combination of the aggregate, cementing agent, sublimation agent,and water can be determined by sampling the mixture from time-to-timeduring the mixing process and examining a sample (e.g., under amicroscope) to determine if the desired level of homogeneous integrationof the different starting materials has been achieved. In an alternativearrangement when the sublimation agent is provided as a paste, the waterand cementing agent can be first mixed, then the sublimation agent addedand mixed, and then the aggregate added and mixed. Other variations forthe adding and mixing of the starting materials can also be used, withthe goal of achieving a homogeneous mixture of the starting materials.

When pre-kilned porous mineral sand is used for the aggregate, themicro-pores on the surface of the aggregate particles (granules) willpull water from the mixture (i.e.,aggregate/cementing-agent/sublimation-agent/water) into the micropores,but the pores are too small to pull in cement and/or sublimation agentsolids. This will promote tighter packing of the grains of the aggregate(which will result in improved sintering, as described more fullybelow), and will also improve workability (for molding) of theaggregate/cementing-agent/sublimation-agent/water mixture. The use ofpre-kilned porous mineral sand for the aggregate, however, may result inlower porosity in the resulting unitized construction material. Unkilnedarkosic micaceous sand can also include naturally occurring sublimationagents (such as metal sulfides), thus assisting in removing calciumcomponents from the cured concrete, and lessening the amount of aseparate sublimation agent to be added to the starting materials (orremoving altogether the need for a supplemental sublimation agent). Insome instances it is desirable that the aggregate of the startingmaterials include a mixture of pre-kilned and unkilned arkosic/micaceoussand, thus deriving a portion of the benefit of each. As can beappreciated, in this way the resulting unitized construction materialcan be engineered for porosity, strength and chemical resistance by theselection of the aggregate and the percentages of each type of aggregateto be used.

The mixture of the starting materials can also be processed (prior tocuring and kilning) by agitating the mixture with a vibrator or the likein order to remove any air particles from the mixture. This will furtherfacilitate saturating the aggregate with free water (and particularlywhen the aggregate is pre-processed in order to provide for surfaceporosity of the aggregate).

Forming the Mixed Starting Materials into the Desired Shape.

Once the desired level of homogeneous integration of the startingmaterials for the desired unitized construction material to bemanufactured from the starting materials has been achieved, then themixture of the starting materials (which is preferably of a generallyflowable or pourable state) can be placed into one or more forms (ormolds) for curing.

In one variation, rather than placing the mixture of the startingmaterials into a mold, the mixture of the starting materials can beextruded into the desired shape of the unitized construction material tobe manufactured from the starting materials. As the mixture of startingmaterials is extruded, the formed extrusion can be cut to the desiredlength for unitized construction material to be achieved. The extrusionprocess of forcing the mixture of the starting materials through a diewill tend to heat the outer surface of the extruded material (due tofriction and the hydration reaction of the curing cement), causing asufficient drying at the surface to allow the extruded mixture to hold ashape such that the curing process can be performed without the use of amold.

Curing the Starting Material within the Mold (or Form).

The curing of the combination of the starting materials within the mold(or molds, or forms) generally follows the process of cement curing(i.e. hydration), and allows the starting materials within the mold (orform) to adhere to one another into a solidified unit which can then beremoved from the mold without damage to the solidified unit of startingmaterials. This solidified unit of starting materials can then be placedinto a kiln for further processing (as described below). The time forcuring the combination of the starting materials for the unitizedconstruction material depends on a number of different factors,including: (i) the maximum thickness of the starting materials withinthe mold (or molds, or forms); (ii) the selected starting materials(including quantity of water and any additional compounds added to thecementing agent, such as curing accelerator compounds, air entrainmentcompounds, etc.); and (iii) the ambient temperature. In general thestarting materials are cured within the mold (or form) for a period oftime which allows the starting materials to solidify to a degree suchthat they can be removed from the form, and transferred to a kiln,without damage to the cured starting materials. Further, as indicatedabove, if the mixture of starting materials is extruded (rather thanbeing formed in a mold), then the curing process can be performedoutside of a mold. Also, in another variation the mold containing thecured starting materials can be placed in the kiln such that the curedstarting materials do not need to be removed from the mold prior tokilning. It will be appreciated that when I refer to the startingmaterials as being or becoming solidified, this means that the unit ofstarting materials can be removed from the mold (or extracted from anextruder) and handled without the shape of the unit becoming distorteddue to a flowing of the starting materials. In certain instancesinterior portions of the formed unit of starting materials can be in aflowable state, but are constrained due to the exterior portions of theunit being in a solidified state. It will further be appreciated thatthe state of being solidified is a relative term, and that somematerials (e.g., glass), which are typically considered in generalparlance to be solid, will in fact will flow, given sufficient time.Accordingly, the use of the terms solid, solidify, solidified, etc.herein does not mean that the unit of starting materials cannot and willnot flow (given sufficient time), but only that the unit of the startingmaterials will retain its shape for a period of time sufficient to allowthe unit of starting materials to be removed from a mold (or anextrusion unit), placed into a kiln, and subsequently kilned.

Kilning of the Cured Starting Materials in Order to Form the UnitizedConstruction Materials.

The formed (solidified) starting materials for the unitized constructionmaterials are placed in a kiln at about ambient temperature (or at atemperature preferably not exceeding about 90° C. (about 200° F.)). Thekiln can be held at a temperature of about 90° C. (about 200° F.) for aperiod of time (e.g., 2 hours per inch of thickness (i.e., maximumdimension)) in order to vaporize water from the solidified startingmaterials. Removal of excess water from the formed (solidified) startingmaterials is desirable to reduce the likelihood of cracking of thesolidified starting materials which can result from rapid vaporizationof water in the solidified starting materials. (Alternately to dryingthe formed (solidified) starting materials in the kiln, they can bedried outside of the kiln prior to kilning to remove water.) The kilntemperature is then increased to a temperature selected to sinter theaggregate granules to one another. Depending on the aggregate beingused, the kiln temperature is increased to a processing temperature ofbetween about 1000° C. and 1250° C., and more preferably between about1065° C. and 1150° C. (about 1950°-2100° F.). When a copper-basedcompound is used as the sublimation-reaction agent, then the kilningtemperature is preferably less than about 1120° C. (about 2050° F.) inorder to avoid melting of di-copper-sulfide (which melts at about 1130°C. (about 2070° F.)). As the kiln temperature passes through thetemperature range of about 450° C. and about 965° C. (about 840° F. toabout 1770° F.) the sublimation agent (for example, molybdenumdisulfide, MoS₂) will oxidize (in the case of molybdenum disulfide, thereaction is to MoO₃), and the oxidized sublimation agent will then reactwith residual lime (e.g., CaO and Ca(OH)₂) from the cementing agentcuring process. For molybdenum disulfide as the sublimation agent andPortland cement as the cementing agent, the reaction isMoO₃+CaO->CaMoO₄. (A stoichiometric equivalent is achieved at about 3parts cement to about 1 part MoS₂ (by weight).) Preferably the rate oftemperature increase for the kiln from the initial temperature to theprocessing temperature is about 260-540° C. (500-1000° F.) per inch,based on the minimum dimension of the formed and cured startingmaterials. Further, as the kiln temperature is increased from theinitial temperature to the processing temperature, the temperature canbe held in a temperature range for sublimation of the sublimation agentto allow a large quantity of the sublimation agent to evolve beforesintering of the aggregate begins. The kiln is held at the processingtemperature for a period of at least about 30 minutes per inch ofthickness (based on the minimum dimension of the formed and curedstarting materials). The kiln can be held at the processing temperaturefor longer periods of time (for example, about one hour per inch ofthickness of the formed starting materials). A longer kilning time atthe processing temperature provides for a higher degree of sintering ofthe aggregate, but also reduces porosity of the formed materials. Thus,the kilning time at the processing temperature is selected based on thedesired properties of the end unitized construction materials. That is,a shorter kilning time (at the processing temperature) is used for aunitized construction material desired to have high porosity butrelatively low crush strength versus a longer kilning time (at theprocessing temperature) for a unitized construction material desired tohave high crush strength but relatively low porosity. After the kiln hasbeen maintained at the processing temperature for the desired period oftime, the kiln can then be cooled to the ambient temperature at a rateof about 540-815° C. (1000-1500° F.) per hour per inch of thickness(minimum dimension) of the unitized construction material.

When micaceous arkose sand is used as the aggregate then the evolutionof muscovite+quartz to K-feldspar+aluminum silicate+steam (orparagonite+quartz to Na-feldspar+aluminum silicate+steam), occurs attemperatures beginning at about 900° C., thus forming porosity andpermeability in the aggregate. The muscovite can be substituted bysericitized or serite mica or other white (low iron) mica. However, inorder to achieve the desired sintering between the aggregate granules,and also between aggregate and cement, a kilning temperature in excessof at least about 1000° C. is desirable or alternately, holding the kilnat a temperature of about 1000° C. for a longer period of time.

In certain instances it is desirable that the kilning of the formed,cured and solidified starting materials for the unitized constructionmaterials be performed under a partial vacuum. This can be accomplishedby providing a kiln that allows for a partial vacuum (i.e., an internalpressure below an ambient pressure of one bar (one atmosphere, or lessthan about 14 psi, or less than about or about 97 kPa) to be achievedwithin the kiln. Placing the kiln under a partial vacuum during kilningof the cured and solidified starting materials can reduce oxidation ofthe sublimation agent, thus increasing the amount of sublimation agent(e.g., molybdenum disulfide) that sublimates directly, and thusincreasing the porosity of the finished unitized construction material.More specifically, and as described above, a sublimation agent ofmolybdenum disulfide (MoS₂) will react (under a temperature of greaterthan about 450° C.) with calcium oxide in the cement to form calciummolybdenum oxide (CaMoO₄). By reducing oxygen within the kiln (either byreducing the atmospheric pressure within the kiln, or by injecting aninert gas within the kiln to displace oxygen), less of this reactionwill occur, and a greater portion of the molybdenum disulfide willsublime directly. (A reduced atmospheric pressure within the kiln ispreferred in this instance, since the lower pressure will tend topromote sublimation.) Direct sublimation of the molybdenum disulfidewill create more inter-granular porosity (i.e., between the aggregategranules) than will the reaction (and subsequentvaporization/sublimation) of CaMoO₄.

The porosity in the final unitized construction material is due to twosources: inter-granular porosity (i.e., pores between sintered faces ofthe aggregate) and porosity of the aggregate. For example, if porousmineral-based sand (as described above) is used for at least part of theaggregate, then the porous mineral sand will provide essentiallymicroscopic (almost molecular level) porosity on the surfaces of theporous mineral sand, as well as porosity throughout the entire matrix ofthe sand grain. This fine porosity not only allows the finished unitizedconstruction material to hold a large quantity of a liquid (such aswater), but can also act as a filter to remove fine solids from theliquid. Beyond porosity, the final unitized construction materials alsoexhibit a high permeability by virtue of interconnected vapor channelswhich are formed during the kilning process (as described below), whichprovides for good fluid conductivity (both liquid and vapor) through thefinal unitized construction materials.

It will be appreciated that a large variety of unitized constructionmaterials can be provided for according to the above description, giventhe large number of variables that can be used in formulating thestarting materials therefore (i.e., including variations in the startingmaterials (e.g., the aggregate, the cementing agent and the sublimationagent), and variations in the kilning temperatures and kilningtemperature regimen). Accordingly, the above method can includeselection of parameters (e.g., starting materials and a kilningtime/temperature regimen) preselected (or engineered) in order toproduce a final unitized construction material conforming to desiredspecifications (e.g., porosity, permeability, chemical composition, andcrush-strength). That is, the above-described process provides methodsfor the manufacturing of various engineered unitized constructionmaterials (i.e., unitized construction materials manufactured accordingto specifically selected specifications with regard to at leastporosity, strength (both tensile and compressive), chemical composition,resistance to chemical attack, and resistance to freeze-thaw breakdown).

Exemplary Description of Porosity Formation for Unitized ConstructionMaterials Using Portland Cement as a Cementing Agent and MolybdenumDisulfide as a Sublimation Agent.

In the instance where the unitized construction materials use Portlandcement as the cementing agent and molybdenum disulfide as thesublimation agent, then the inter-granular porosity (i.e., pores formedbetween granules of the aggregate, versus pores formed on the surface ofthe aggregate) is formed by the sublimation and/or vaporization ofcomponents between the aggregate granules, coupled with the sintering ofthe aggregate granules to one another as well as the cement. Morespecifically, the sintering (which mostly occurs between about 1040° C.and about 1250° C. (about 1900° F. and 2280° F.) is the result of: (i)fusing of quartz in the aggregate; (ii) fusing of feldspar sand (whenused for, or as a part of, the aggregate, and especially sodic and/orpotassic components thereof, or resulting from the thermal decompositionof mica within the aggregate); (iii) calcium silicate in the curedcement; (iv) any residual calcium molybdnate (which results fromreaction of molybdenum disulfide sublimation agent with the calciumcomponents in the cured cement); and (v) zinc sulfide (ZnS), and othervolatile metal sulfides, which may be present in unfired felsic sandused in the aggregate, or in fired sand that has been recrushed (asdescribed above). In any event, it is desirable to hold the kilningtemperature somewhat lower than the softening temperature of feldspar(about 1250° C.) in order to avoid the feldspar becoming liquid and thusblocking flow channels when cooled. At the preferred sinteringtemperature a partial melting of the sodic and/or potassic elements inthe feldspar aggregate allows sintering to occur. Further, solidsintering of silica, aluminum silicate and calcium silicate occurs, aswell as plastic deformation and partial sublimation of any exposed zincsulfide. As described above, the finished unitized constructionmaterials provided for herein can include two kinds of porosity: (i)aggregate porosity (i.e., porosity on the surfaces and within the matrixof the aggregate); and (ii) inter-granular porosity (i.e., porositybetween the granules of the aggregate and/or the cured cement. Theporosity is provided by pores which can have dimensions (i.e., width anddepth) of about between about 10 nanometers and about 100 nanometers orless. The porosity of the unitized construction materials results from(i) sublimation and/or consolidation of metallic components (such aszinc sulfide and other volatile metal sulfides) on exposed surfaces, andwithin the matrix, of the aggregate and the cured (hydrated) cementingagent during kilning of the starting materials used for the unitizedconstruction materials; (ii) sublimation and/or consolidation of calciumcomponents (which are a result of the cement curing hydration process)during kilning of the starting materials; (iii) the formation of pores(and channels) between adjacent components of the starting materialsduring the kilning process; and/or (iv) the sintering process whichoccurs (during kilning) between the aggregate, the cured cementingagent, and compounds evolved (i.e., generated) as a result of chemicalinteractions between the sublimation agent (or sublimation-reactionagent) during the kilning process. When the aggregate includes micaceouscomponents (or other components, as described herein) which act asprecursors to feldspathic compounds, then the reaction (as describedabove) tends to generate steam as a byproduct. The evolution of thesteam (and other volatile compounds) from the solidified unit of thestarting materials and into the kiln forms flow channels within thesolidified unit. These flow channels provide for permeability in thefinished units of the construction materials. The high porosity, coupledwith the high permeability, provide for finished unitized constructionmaterials which can pass large volumes of fluids, as well as entrainlarge volumes of liquids.

As indicated herein, in order to manufacture a unitized constructionmaterial having high porosity, high permeability, and high strength, anaggregate which includes micaceous components as well as quartziticcomponents is desirable. The ratio of micaceous components andquartzitic components within the aggregate is preferably on the order ofabout 1:1 (on a ground-mass basis). (This ratio allows for a gooddistribution of bonding, by sintering, of resulting felspathiccomponents to quartzitic components within the mixture.) This desiredratio of micaceous components to quartzitic components can be found incertain native rocks (e.g., the Precambrian rocks of the Burkeformation). However, when native rocks having this desired combinationare not available, then the available source rock used for the aggregatecan be supplemented by providing mica and/or quartz in order to achievethe desired ratio. In any event, the conversion process from themicaceous and quartzitic components, in the presence of the cured (i.e.,hydrated) cement components, is believed to occur as follows during thekilning process. Initially, the micaceous components within theaggregate are converted into feldspar, water, aluminum silicate andmetal sulfides. (The conversion of micaceous components within theaggregate into feldspathic components does not result in the removal ofany elements by sublimation or the like, but rather results in thegeneration of denser chemical compounds within the matrix of theaggregate, thus creating porosity throughout the aggregate.) Then thewater and metal sulfides pick up the calcium components (i.e., calciumoxide and calcium hydroxide) which were generated by the cement duringthe hydration (i.e., curing) process, and these calcium components areremoved by sublimation and/or vaporization (as calcium metal oxides orotherwise). The remaining forms of calcium left in the unitized formedconstruction material (e.g., calcium silicate and calcium-metal-sulfidesthat don't sublime) are generally non-reactive forms of calcium, thusimproving resistance to chemical attack of the formed constructionmaterial from components such as ice melters and the like. Further,during the kilning process, the resulting feldspathic components sinterwith the quartzitic components of the aggregate in order to form astrong unitized construction material.

It will be appreciated that the unitized construction materials providedfor herein differ significantly from prior art unitized constructionmaterials (such as clay-based kilned bricks and cement-based bricks).Specifically, the unitized construction materials provided for hereincan have very high tensile and compressive strengths, along with highpermeability and/or porosity. More specifically, prior art unitizedconstruction materials manufactured by a cementing process (i.e., cementand aggregate, to form concrete) derive their strength from the chemicalhydration reaction of the cement materials on the aggregate (typicallysand or gravel). By comparison, the unitized construction materialsprovided for herein derive their strength primarily from the sinteringof the aggregate and/or pre-cured cement particles to one another, whichprovides a much greater strength (tensile and compressive) over priorart cemented unitized construction materials. Further, prior artunitized construction materials manufactured by a cementing processprovide for a much lower permeability and/or porosity than can beachieved using the processes described above for the unitizedconstruction materials provided for herein. A still further advantage ofunitized construction materials provided for herein over prior artcemented unitized construction materials is that the unitizedconstruction materials provided for herein provide enhanced resistanceto degradation from exposure to chemicals (such as ice melters and thelike, which can attack the calcium oxide in cured cement) due to (i) themuch lower quantity of cement used in the preparation of the comparablestarting materials (and thus, less resulting calcium oxide); and (ii)the fact that the cured cement component most susceptible to chemicalattack (i.e., calcium oxide) tends to be removed from the unitizedconstruction materials provided for herein by the reaction process witha sublimation agent. Additionally, the unitized construction materialsprovided for herein have increased resistance to degradation by fireover prior art concrete-based unitized construction materials. That is,the large quantity of cement present in prior art concrete-basedunitized construction materials makes them susceptible to calcination attemperatures above about 750° C. (and thus, weakening of the overallmatrix) when exposed to high temperatures, whereas the low percent ofcalcium oxide in the unitized construction materials provided forherein, as well as the high-temperature sintering of the aggregate,makes the unitized construction materials provided for herein extremelyresistant to fire temperatures up to about 980° C. (about 1800° F.).

Additionally, prior art unitized construction materials manufactured bya kilning process (such as bricks, including those manufacturedaccording to the process described in U.S. Pat. No. 7,621,692) differfrom the unitized construction materials provided for herein at least inthat: (i) the unitized construction materials provided for herein caninclude a much greater degree of overall porosity (due to the ability toprovide micro-pores on the surfaces, and within the matrix (i.e.,lattices) of the aggregate prior to kilning resulting from using anon-kilned micaceous arkosic sand (or other suitable aggregatematerials, as described above) as at least a portion of the aggregate,as well as to the sublimation of the sublimation agent during kilning);(ii) the unitized construction materials provided for herein include amuch higher degree of permeability (or water conductivity) as comparedto the prior art; (iii) the unitized construction materials provided forherein can be formed in more complex shapes due to the pourable natureof the starting materials (versus being restricted to a shape that canbe compressed within a mold without extraordinary additional processingsteps); and (iv) the unitized construction materials provided for hereinallow for a smooth finished surface and edges (due to the workability ofthe starting materials, as aided by the uncured cement and thesublimation agent), as opposed to prior art compaction of clay. Of note,prior art porous ceramic unitized construction materials aremanufactured by consolidating the starting materials using high pressurecompaction (which generates a porous matrix of the starting materials),and then subjecting the consolidated unit to high temperature to fuseadjacent grains to one another. In this prior art process, no porositywithin the grains themselves is achieved due to the selection of thestarting materials (i.e., clay and quartz-based sand), or as a result ofkilning the consolidated unit of the starting materials. In fact, aprior art consolidated unit of starting materials is less porous, andless permeable, after kilning than before kilning due to grains of thestarting materials sintering to one another and progressive closing ofair gaps between grains. By comparison, the method of manufacturingunitized construction materials of the current disclosure begins byfirst forming a flowable paste of the starting materials (i.e., theaggregate, the water and the cement), and then placing this paste into amold. At this point the paste within the mold has essentially nopermeability whatsoever. (Recall that the aggregate is preferably offine, almost powder-like, consistency.) During the curing process (i.e.,hydration of the cement), the paste becomes a solid unit, still havinglittle or no porosity. It is only during the subsequent kilning processthat the porosity results from (i) transformation of any micaceouscomponents within the aggregate into felsic (and other) components, (ii)sublimation of metal sulfides from the aggregate, (iii) scavenging ofcalcium components (which resulted from the hydration reaction of thecement), (iv) vaporization of any water (either original or generated bysubsequent chemical reaction), and (v) sintering of the evolved (ororiginal) felsic components with adjacent quartz grains. Still further,when a prior art consolidated unit of starting materials is then kilned,the resulting unit is reduced in size (in all dimensions) by asignificantly measurable amount as a result of the sintering process. Bycomparison, the end product units of unitized construction materials ofthe present disclosure are much less reduced in size from theirpre-kilned size. Further, with respect to item (ii) above regardingenhanced permeability of the unitized construction materials providedfor herein over the prior art, during the kilning process of thestarting materials water and other volatile components (includingsublimation components) are evolved, and thus are released from themixture of the starting materials by forming vapor passageways whichallow the volatile components to be released from the startingmaterials. (This process of forming fluid passageways, or permeability,is further facilitated by sublimed metal sulfides chemically bindingwith calcium components from the hydrated cementing process andsubsequently evolving from the starting materials in a gaseous form.) Itis the formation of these fluid passageways within the kilned startingmaterials which results in the enhanced permeability over the prior artof the end product of unitized construction materials of the presentdisclosure. This enhanced permeability can be exhibited as waterconductivity and/or any fluid conductivity through the end product unitsof unitized construction materials of the present disclosure. However,water conductivity through the end product units of unitizedconstruction materials of the present disclosure is particularlyenhanced over the prior art by virtue of capillary interaction betweenwater molecules and the interconnected micro-pores of the unitizedconstruction materials, In fact, the water conductivity of the endproduct units of unitized construction materials of the presentdisclosure actually increases over time once the micro-pores of theunitized construction materials become wetted due to this capillaryactivity, as well as subsequent gravity flow through the interconnectedflow channels within the matrix of the end product units. By comparisonwater conductivity of prior art porous unitized construction materialsdecreases over time as the matrix of pores becomes water filled.

The unitized construction materials provided for herein can include thefollowing additional advantages over prior art unitized constructionmaterials: (i) decreased density (and thus, overall weight forcomponents of essentially identical dimensions) due to the increasedporosity in the unitized construction materials provided for herein;(ii) increased ability to retain and/or pass water (or other liquids)due to increased porosity and permeability that can be provided for inthe unitized construction materials provided for herein; (iii) improvedsound insulation properties (due to higher occurrence of void spacewithin the unitized construction material); (iv) improved thermalinsulation properties (assuming the outer surfaces are sealed by acovering, thus preventing thermal convection); and (v) improved surfaceadherence of paints, stains, adhesives, etc. due to surfacemicro-porosity that can be provided by the unitized constructionmaterials provided for herein. As described above, by selection of thestarting materials and the kilning temperature regimen (and inparticular, the duration of the sintering time), the unitizedconstruction materials provided for herein can be engineered forspecific intended uses. Thus, for example, if the intended use of theunitized construction materials is for a structural beam, thenpermeability is generally not a consideration, and the startingmaterials can be kilned for a longer sintering period of time (ascompared to a unitized construction material where high permeability isdesired). This will result in a structural beam that is much lighter inweight, and at least as strong (in tension and compression) as a priorart beam formed using a concrete-based manufacturing process.

Example I: Fabrication of Porous Unitized Formed Mineral-BasedConstruction Materials Using Micaceous Arkosic Sand

In one example two blocks were fabricated using the above-describedprocess, both blocks having the following dimensions: 10 cm×10 cm×4 cm.The first block was fabricated using porous mineral based sand (asprovided for herein above) as the aggregate, and the second block wasfabricated using more than 80% of unkilned mineral based micaceousarkosic sand as the aggregate. (The starting material sand used in bothinstances was the same—micaceous arkose based sand—with the differencebeing that the sand for the first block was pre-kilned to increaseporosity on the surfaces of the sand.) Both blocks used a mixture ofPortland cement and molybdenum disulfide in a mixture of 60 grams ofcement to 20 grams of molybdenum disulfide paste. Both blocks were firedin a kiln at the same temperature and for the same period of time. Afterremoving the blocks from the kiln the first block (using the porousmineral based sand) weighed 765 g, and the second block (usingnon-kilned sand) weighted 783 g. Further, the first block was found tohold 92 g of water, and the second block was found to hold 60 g of water(i.e., a 50% increase in water absorption by using the pre-kilned porousmineral based granular sand aggregate). However, the block fabricatedusing non-kilned sand is expected to have higher permeability over theblock fabricated using pre-kilned sand, due to the formation ofinterconnected fluid flow channels resulting from the transformation ofmicaceous components within the aggregate into felspathic components andwater vapor which creates the flow channels, and the evolution ofmetallic components which creates porosity on (and within) the grains ofthe starting materials.

Example II: Comparison of Porous Unitized Formed Mineral-BasedConstruction Materials Using Micaceous Sand with Prior Art Ceramic TileMaterial

In the second example test samples of porous unitized constructionmaterials were fabricated using a method provided for herein (with theaggregate having greater than 50% ground mass of micaceous arkosic sandas the aggregate), and the results compared with similar sized prior artporous ceramic materials (generally fabricated as provided for in U.S.Pat. No. 7,621,692). The test samples were sized as follows: forcompressive strength tests, tile dimensions were 100 mm×100 mm×40 mm;for water conductivity tests, tile dimensions were 100 mm diameter×40 mmthick. The test tiles according to the present disclosure werefabricated as follows:

-   -   Aggregate: 1500 gm micaceous arkose sand (no pre-kilning),        approx. 50% (ground mass) muskovite mica, graded to +200/−18        mesh, with an average aspect ratio of about 3:1;    -   Cement: 180 gm Portland cement;    -   Sublimation agent: 60 gm molybdenum disulfide;    -   Water: 400 gm*.    -   Heating: test tiles were placed in a kiln and the kiln        temperature was increased at rate of 450° F. per hour to a        temperature of 2050° F., then held at 2050° F. for 1.75 hours;        then cooled at rate of about 750° F. per hour.    -   Total water, including any free water present in the aggregate.

Test results: the results of various tests on the porous tilesfabricated according to the current disclosure, and the prior art porousceramic tiles, are as follows:

Tiles of the present disclosure Prior art tiles Water capacity: 110 gm(~27.5% vol)* 80 gm (~20% vol) Compressive strength: 8800 psi 8500 psiWater conductivity** 7 inches/hr 1.7 inches/hr *About 400 ml **Based ona constant water column of 30 inches

The results indicate that the porous construction materials of thepresent disclosure have a much higher rate of water conductivity (i.e.,permeability) than do prior art porous tiles having comparablecompressive strength. It is contended that the feldspar (resulting fromthe muscovite+quartz->K-feldspar+aluminum silicate+steam reaction) actedas the primary sintering agent between the particles of aggregate, andbetween aggregate and concrete. Further, the majority of the porosityand the permeability is contended to result from this reaction,supplemented by the liberation of calcium oxide (and calcium hydroxide),and the sublimation of metal oxides formed from metal sulfides.

Example III: Comparison of Porous Unitized Formed Mineral-BasedConstruction Materials Using Micaceous Sand, and No Sublimation Agent,with Prior Art Ceramic Tile Material

Another test was performed along the lines of Example II, but in thethird example no sublimation agent was used. All of the startingmaterials for the test tiles according to the present disclosure werethe same as in Example II (with the exception that the quantity of waterwas increased by not more than 20%), and no sublimation agent was used.The test results were as follows:

Tiles of the present disclosure Prior art tiles Compressive strength:3100 psi 8500 psi Water conductivity* 7.4 inches/hr 1.7 inches/hr *Basedon a constant water column of 30 inches

In this third example it is believed that the calcium silicate (CaSiO)of the cement is sintered to adjacent particles of the sand aggregate(thus chemically bonding the calcium silicate to provide enhancedresistance to chemical degradation due to exposure to chemicals such asice melters), and the calcium oxide is removed via the reaction withnaturally occurring sublimation agents within the aggregate and thecement (in the manner described above).

Example IV: Same as Example II, but Using Anhydrous Copper asSublimation Agent

In this example a unitized construction material was fabricated asfollows:

-   -   Aggregate: 750 gm micaceous arkose sand (no pre-kilning),        approx. 50% (ground mass) muskovite mica, graded to +200/−18        mesh, with an average aspect ratio of about 3:1;    -   Cement: 90 gm Portland cement;    -   Sublimation agent: 60 gm copper sulfate;    -   Water: 200 gm.    -   Heating: test tiles were placed in a kiln and the kiln        temperature was increased at rate of 450° F. per hour to a        temperature of 2050° F., then held at 2050° F. for 1.75 hours;        then cooled at rate of about 750° F. per hour.

Test results: the results of various tests on the porous tilesfabricated according to the current example, and the prior art porousceramic tiles, are as follows:

Tiles of the present disclosure Prior art tiles Water capacity: 110 gm(~27.5% vol)* 80 gm (~20% vol) Compressive strength >9000 psi 8500 psiWater conductivity** >25.0 inches/hr 1.7 inches/hr *About 400 ml **Basedon a constant water column of 30 inches

In this fourth example it is believed that the copper reacts with aportion of the calcium oxide in the cement to form calcium coppersilicate. The copper in the copper sulfate does not appear to sublime insignificant quantities, but rather facilitates sublimation (andvaporization) of other compounds. Further, the calcium copper silicateis believed to facilitate in sintering, thus accounting for the highercompressive strength over the use of molybdenum disulfide.

In yet another example (generally corresponding to the parameters ofExample II) the amount of a sublimation agent was reduced, and thesintering time was increased, resulting in a test tile having acompressive strength of 12,000 psi and a water conductivity ofapproximately 2 inches of water per hour. In this example the rate ofwater conductivity is generally the same (or slightly greater) than theprior art porous tiles (1.7 inches per hour), but the compressivestrength of the tiles is increased by more than 40% over the compressivestrength of the prior art porous tiles.

From the examples provided above it can be appreciated that porousmineral-based construction materials (such as tiles and the like)manufactured according to methods provided for herein provide forsubstantially increased rates of water conductivity, while providingsimilar strength to prior art porous mineral-based constructionmaterials. Further, as can be appreciated by the examples, the porousmineral-based construction materials provided for by the presentdisclosure can be provided as engineered materials—i.e., desiredproperties of water conductivity and strength can be selected, and thenthe porous mineral-based construction materials can be fabricated toachieve the desired properties by varying the starting materials (e.g.,type of aggregate to be used), the kilning time, and the inclusion (oromission) of a sublimation agent (among other variables provided forherein).

Inclusion of Reinforcing Elements into the of Unitized ConstructionMaterials.

As indicated above, the starting materials for the unitized constructionmaterials can include reinforcing elements. The reinforcing elements arepreferably provided as high temperature metal components, and caninclude metal fibers and metal structural elements. In one example thereinforcing elements can include steel fibers (and more preferably, highchromium stainless steel fibers). The size (length and diameter) of thesteel fibers will depend on the size of the unitized constructionmaterial being fabricated. Preferably, the steel reinforcing fibers havea diameter of about 1 mm or less. The steel reinforcing fibers can beadded as either straight fibers, or as bent or coiled lengths of fiber.In another example the reinforcing elements can include steel members(and more preferably, high chromium stainless steel members), andpreferably having a diameter of between about 5 mm and 25 mm, dependingon the size of the unitized construction material being fabricated. Suchreinforcing steel members can be provided as bar material, and can thusbe considered as reinforcing bar, or as rebar. (The reinforcing memberscan also be fabricated from non-ferrous metals and metallic alloys.) Thelength of the rebar material used as reinforcing steel members willdepend on the overall size (length, width and depth) of unitizedconstruction materials being fabricated. Preferably, the steel rebarmaterial to be used for reinforcing the unitized construction materialsis a high chromium stainless steel in order to resist thermo-chemicaldegradation during the kilning process, as well as to resist detemperingof the rebar material. When placing steel rebar into the initial mixtureof starting materials for the unitized construction materials beingfabricated, certain considerations should be taken into account.Specifically, the linear thermal coefficient of expansion for stainlesssteel (about 15×10⁻⁶ m/(m K)) is generally greater than the linearthermal coefficient of expansion for the aggregate (about 6×10⁻⁶ m/(mK)). Thus, there is a risk that during kilning of the starting materials(for the unitized construction materials) the steel rebar will expand atsuch a rate (as compared to the surrounding aggregate materials) thatthe steel rebar will cause fracturing of the surrounding sinteringaggregate material. In order to address this concern the rebar can firstbe coated with an envelope of expansion material which becomes plasticprior to the sintering temperature of the surrounding matrix materialswithin the kiln, thus allowing the rebar to expand within the envelopeof the coating material, and reducing the presentation of harmful anddestructive stress on the surrounding sintering aggregate. In oneexample the envelope of expansion material is provided as felsic sandmaterial (e.g., a fine grade felsic sand), which can be applied over therebar by dipping the rebar into a mixture of the felsic sand and anadhesive (such as a high viscosity grease). Preferably the rebar isprovided with a coating of the expansion material which is at leastabout 25% of the thickness of the rebar. More preferably the rebar isprovided with a coating of the expansion material which is at leastabout 75% to 125% of the thickness of the rebar. For example, a steelrebar having a nominal diameter of about 0.25 inches (about 6 mm) can becoated with a felsic expansion envelope material having a thickness offrom about 0.125 inches (about 3 mm) to about 0.375 inches (about 9 mm).The felsic material can be potassic-feldspar powder, for example. Thecoating of the expansion material further extends to end portions of therebar to accommodate longitudinal expansion of the rebar during thekilning of the unitized construction materials. The felsic expansionenvelope will sinter to the surrounding aggregate during the kilningprocess. The reinforcing bar material can include threaded bar material,which facilitates engagement of the reinforcing bar material (i.e.,rebar) with the surrounding expansion material. This arrangement isdescribed further below and with respect to FIG. 3.

In another variation the solidified unit of the mixture of startingmaterials can be provided with reinforcing materials prior to placingthe consolidated unit of the mixture of starting materials into thekiln. (That is, the reinforcing materials are placed into the curedstarting materials following curing, and prior to kilning.) This can beaccomplished by drilling (or otherwise forming) one or more holes intothe solidified unit of the mixture of starting materials, injecting agrout or expansion material into the holes formed within the solidifiedunit of the mixture of starting materials, and thereafter placing areinforcing bar material (or other reinforcing material) into the holes.In a further variation the reinforcing materials (or reinforcingmembers) can be placed into the resultant unitized constructionmaterials (i.e., following the kilning process described above) byforming holes in the resultant unitized construction materials, fillingthe holes with a grout or the like, and then placing a reinforcingmember into the grouted hole.

It can be desirable to add steel reinforcing bar material after kilningof the starting materials since the heat of kilning can anneal the steelin the rebar, thus reducing the tensile strength thereof. In thisinstance (i.e., post-kilning reinforcing using rebar) holes for therebar (and for a grout to hold the rebar in place) can be formed in thefinished unitized construction materials (as indicated above), or theycan be formed in the molded starting material prior to kilning. Forexample, holes (for rebar material, and associated grouting material)can formed in the mixture of starting materials by: (i) drilling orwater jetting holes into the cured mixture of starting material prior tokilning; (ii) placing a hole-forming bar material (such as a metal bar)into a mold prior to placing the mixture of starting materials into themold (as described more fully below); (iii) placing a sacrificialhole-forming bar material into a mold prior to, or as part of thesequence of, placing the mixture of starting materials into the mold (asalso described more fully below); and (iv) forming the holes for groutand rebar as part of an extrusion process for forming the mixture of thestarting materials into a form that can be cured and then kilned.

FIG. 3 is a sectional side view of a unitized formed constructionmaterial 120 which includes the mixture of starting materials 122 and asteel reinforcing bar member 123 placed within the mixture of startingmaterials. The steel reinforcing bar member 123 is surrounded by anenveloped of felsic coating material 124. The felsic coating material124 becomes plastic during kilning of the unitized formed constructionmaterial 120, thus allowing the steel reinforcing bar member 123 tothermally expand without compromising the integrity of the surroundingmixture of starting materials 122. During kilning the felsic coatingmaterial 124 will sinter and bond with aggregate in the mixture ofstarting materials 122, and during cooling the felsic coating material124 will adhere to the steel reinforcing bar member 123, thus forming amechanical connection (via the felsic coating material 124) between thestarting materials 122 and the reinforcing bar member 123. Preferably,the reinforcing bar member 123 includes surface features (such asthreads or furls, as depicted in FIG. 3) to facilitate engagement of thefelsic coating material 124 with the reinforcing bar member 123 when theunitized formed construction material 120 is cooled and the felsiccoating material 124 solidifies. Further, during cooling the reinforcingbar member 123 will thermally contract, placing the unitized formedconstruction material 120 into a prestressed compressive state.

FIG. 4 is a sectional plan view of a mold 10 which contains a mixture ofthe starting materials 122 used to form a unitized formed constructionmaterial 150. The mold 10 includes side members 12 and end members 14which contain the mixture of the starting materials 122 within the mold.(The mold 10 also includes a bottom member, not shown, which is attachedat lower edges of the side members 12 and the end members 14 in order toform the mold 10 which contains the mixture of starting materials 122.)The side members 12 of the mold 10 include side member openings 16, andthe end members 14 of the mold 10 include end member openings 18.Vertical hole-forming bar members 22 and 24 are placed through the moldside member openings 16, and horizontal hole-forming bar members 28 and30 are placed through the mold end member openings 18. (The hole-formingbar members 22, 24, 28, 30 can be placed into the mold 10, as depictedin FIG. 4, either prior to placing the mixture of starting materials 122into the mold, or after placing the mixture of starting materials 122into the mold (and prior to curing of the mixture of startingmaterials). As suggested by FIG. 4, the horizontal hole-forming barmembers 28 and 30 can be spaced at an essentially equal verticaldistance from the bottom member of the mold (not shown), and thevertical hole-forming bar members 22 and 24 can be staggered in verticaldistance from the mold bottom member, such that the left-most verticalhole-forming bar member 22 passes beneath the horizontal hole-formingbar members 28 and 30, and the right-most vertical hole-forming barmember 24 passes above the horizontal hole-forming bar members 28 and30. This described arrangement of the horizontal and verticalhole-forming bar members (22, 24, 28, 30) results in horizontal andvertical interleaving of the hole-forming bar members. Diagonalinterleaving of the horizontal and vertical hole-forming bar members 22,24, 28, 30 can be achieved by positioning the opposing openings 16 inthe mold side members 12 at different vertical elevations, and alsopositioning the opposing openings 18 in the mold end members 14 atdifferent vertical elevations. Following kilning of the mixture ofstarting materials 122 in the mold 10, the hole-forming bar members 22,24, 28, 30 can be mechanically extracted from the resulting unitizedformed construction material 150, resulting in openings within theunitized formed construction material that can be filled with grout andreinforcing bar material. Preferably, the hole-forming bar members (22,24, 28, 30) are coated with a grease (such as a molybdenum grease) tofacilitate extraction thereof from the kilned unitized formedconstruction material.

In one variation on the arrangement depicted in FIG. 4, the hole-formingbar members 22, 24, 28, 30 can be sacrificial hole-forming bar material.Sacrificial hole-forming bar material can be fabricated from componentsthat melt, dissolve, sublimate and/or vaporize below the temperature atwhich the sublimation agent sublimes. Examples of components that can beused for sacrificial hole-forming bar material include biodegradableplastics, starch-based materials, and paraffin and wax based materials.Such sacrificial hole-forming bar materials can be placed into the mold10 depicted in FIG. 4, which includes the openings 16, 18 in therespective sides 12 and ends 14 of the mold 10. In this instance (i.e.,of providing the openings 16, 18 in the mold), the sacrificialhole-forming bar materials can exit via the openings during kilning ofthe mixture of starting materials. In an alternative configuration, themold 10 can be provided without the openings 16, 18 in the mold, inwhich instance the sacrificial hole-forming bar materials typicallyvaporize and exit the mixture of starting materials through permeabilitychannels formed in the mixture of starting materials as part of thekilning process.

Pre-Stressing of Unitized Construction Materials.

Following the above discussion for providing reinforcing steel bars intothe starting materials (pre-kilning) for the unitized constructionmaterials, and the differential rates of thermal coefficients ofexpansion between steel and the surrounding aggregate, as the kilnedmaterials (including the rebar and the felsic expansion envelopematerial) are cooled, the steel rebar will contract at a rate fasterthan the thermal contraction of the surrounding aggregate. Thus, thethermally contracting steel rebar will tend to place the surroundingsintered aggregate into compression, thus imposing a pre-stress onresulting unitized construction material. By appropriate selection ofthe reinforcing material, and the thickness of the expansion envelopematerial, engineered pre-stress rates can be imposed on the resultingunitized construction material.

Clay-Based Unitized Formed Construction Materials.

In a variation on the method described above, unitized formedconstruction materials can be manufactured using clay as the aggregate.One source of clay can be recycled clay bricks. In this instance thestarting materials include clay (preferably crushed to a particle sizeof fine to medium sand, as described above), a cementing agent, asublimation agent, and water. The cementing agent is preferably Portlandcement, and the sublimation agent can be molybdenum disulfide (MoS₂)provided in a paste form, or a copper-based solution such as coppersulfate (CuSo₄). The cementing agent can be provided as, for example,between about 8% and about 10% by weight of the clay, and thesublimation agent can be, for example, about 50% by weight of thecementing agent. The water can be mixed with the cementing agent, andthen the paste-form of the sublimation agent can be added and mixed withthe water-cement mixture. The clay aggregate can then be mixed with thewater-cement-sublimation-agent mixture. The resulting mixture of thestarting materials can then be formed in molds (as described above), oris preferably formed by an extrusion process (also described above). Theresulting formed mixture of the starting materials is then dried andcured (which can be performed at ambient conditions), and afterwardskilned. The preferred kilning temperature when clay is used as theaggregate is about 1177° C. (about 2150° F.) when using molybdenumdisulfide as a sublimation agent), and about 1120° C. (about 2050° F.)when using copper sulfate as a sublimation-reaction agent.

I have discovered that adding cementing agent and sublimation agent toclay aggregate will reduce drying time for the formed unitized formedconstruction materials prior to kilning. Further, the addition of thesublimation agent reduces the amount of calcium oxide present in thepost-kilned clay-based unitized formed construction material, due to thereaction of the calcium oxide (CaO) with the molybdenum disulfide (MoS₂)sublimation agent (resulting in calcium molybdenum oxide (CaMoO₄), whichsublimates during kilning, as discussed above). The reaction alsoproduces excess calcium, which can then react with silicon in the clayto form calcium silicate (Ca₂SiO₄). The removal of calcium oxide makesthe brick-like unitized formed construction material more chemicallyresistant to components such as ice melts, and the generation of calciumsilicates in the end product can increase fire resistance and heatinsulative properties.

Method for Manufacturing Unitized Formed Mineral-Based ConstructionMaterials.

As described above, the present disclosure provides for a method formanufacturing (i.e., making) unitized formed mineral-based constructionmaterials. The method can include the following steps: (i) providingstarting materials comprising an aggregate, a cementing agent, asublimation agent and water; (ii) mixing the starting materials with oneanother to achieve a mixture of the starting materials; (iii) placingthe mixture of the starting materials into a form (or mold); (iv) curingthe mixture of starting materials in the form for a period of timeselected to allow the mixture of starting materials to become asolidified unit of the mixture of starting materials, the solidifiedunit of the mixture of starting materials being defined by a minimumdimension of thickness, length, width or diameter; (v) removing thesolidified unit of the mixture of starting materials from the form; (vi)placing the solidified unit of the mixture of starting materials into akiln; (vii) heating the kiln containing the solidified unit of themixture of starting materials to a processing temperature of betweenabout 1000° C. and about 1350° C. and maintaining the kiln at theprocessing temperature for a period of time of between about 10 minutesand about 60 minutes per centimeter of the minimum dimension of thesolidified unit of the mixture of starting materials; and (viii)removing the solidified unit of the mixture of starting materials fromthe kiln. It will be appreciated that the process as just described caninclude additional and alternate steps to those described, as well asvariations on the recited steps. For example, in certain instances thesolidified unit of the mixture of starting materials do not need to beremoved from the form prior to placing the solidified unit of themixture of starting materials into the kiln—i.e., the form containingthe solidified unit of the mixture of starting materials can be placeddirectly into the kiln.)

FIGS. 2A and 2B together provide a flowchart 200 depicting an exemplarymethod for manufacturing unitized formed mineral-based constructionmaterials according to at least one method provided for herein. (It willbe appreciated that the flowchart of FIGS. 2A and 2B depict only oneexample of a method for manufacturing unitized formed mineral-basedconstruction materials according to the methods provided for herein, andthat the method depicted in FIGS. 2A and 2B can include fewer steps thanare indicated, as well as additional steps not shown). In the exemplarymethod depicted in the flowchart 200 of FIGS. 2A and 2B formanufacturing unitized formed mineral-based construction materials, theprocess begins at step 202 (FIG. 2A) by providing starting materialsthat include an aggregate, a cementing agent, a sublimation agent, andwater. At step 204 the cementing agent and the sublimation agent aremixed together to form a mixture of the cementing agent and thesublimation agent. At step 206 the mixture of the cementing agent andthe sublimation agent are mixed with the aggregate, and then at step 208the water is mixed into the mixture of the cementing agent, thesublimation agent and the aggregate. (It will be appreciated that thesteps (i.e., steps 204-208) of mixing the aggregate, the cementingagent, the sublimation agent, and the water can alternately be performedin various sequences and/or combinations, but the overall objective isto mix the starting materials into a homogeneous mixture so that whenthe cementing agent cures the resulting solidified unit (see step 212)is an essentially homogeneous unit.) Following mixing of the startingmaterials, at step 210 the mixture of the starting materials is placedinto a form. At step 212 the mixture of the starting materials in theform is cured for a period of time selected to allow the mixture of thestarting materials to become a solidified unit (i.e., capable of beingremoved from the form and retaining the shape of the form). Then at step214 (FIG. 2B) the solidified unit (i.e., cured product) of the mixtureof the starting material is removed from the form, and at step 216 thesolidified unit is placed into a kiln. (It will be appreciated that thestep of removing the solidified unit from the form, i.e., step 214, isoptional, and that the cured starting materials can be placed into thekiln (at step 216) while still in the form.) Once the solidified unit ofthe starting materials is placed into the kiln, then at step 218 thekiln is heated to a processing temperature of between about 1000° C. andabout 1350° C. and maintained at the processing temperature for a periodof between about 10 minutes and 60 minutes per centimeter of minimumdimension of the solidified unit of the mixture of starting materials.Following kilning of the solidified unit of the starting materials atthe processing temperature for the designated period of time, then atstep 220 the kilned solidified unit of the mixture of starting materialsis removed from the kiln as the unitized formed mineral-basedconstruction material.

Alternative Method for Manufacturing Unitized Formed Mineral-BasedConstruction Materials.

Another method for manufacturing unitized formed mineral-basedconstruction material is similar to the first method described above,except that a separate sublimation agent is not used as a separatestarting material. Rather, I have discovered that Portland cement, aswell as micaceous arkosic sand, contain a certain amount of metalsulfides (including metal disulfides—I will use the term metal sulfidesherein to cover all forms of metal and alkyl sulfides—and also includingsilicate and oxide based metal sulfides). These metal sulfides in thecement, along with metal sulfides on the surfaces (at least) of theaggregate, perform the function of a sublimation agent. That is, at asufficiently high kilning temperature (i.e., about 1120° C. to about1135° C. (about 2050° F. to about 2075° F.)) these metal sulfidesvaporize and/or sublimate, leaving porosity not only on the surfaces (atleast) of the aggregate, but also between grains of the cement and theaggregate. This porosity not only provides for liquid permeability inthe resulting unitized construction material, but also reduces density(and thus weight) of the unitized construction material. In addition,the kilning temperature is selected to cause sintering of grains of theaggregate to one another, thus providing tensile and compressivestrength to the resulting unitized construction material. Further, asdescribed herein, the sublimation process of the metal sulfides from thecement and the aggregate is the result of a chemical process which tendsto remove calcium components (such as calcium oxide), thus providing forincreased resistance to chemical breakdown due to exposure to materialssuch as ice melters and the like. More specifically, one such chemicalreaction which occurs during kilning of the starting materials is asfollows: CaO+MS_(x)+O₂->CaMO_(x)=SO_(x) (where “M” is used to indicate ametal, including alkyl metals such as lithium, sodium, manganese, andpotassium; MS_(x) thus designates any metal sulfide component thereof).

In this variation the preferred aggregate is micaceous quartzite whichcan decompose to feldspar (or arkose-based feldspar), and morepreferably one of these components having about 6% or more of potassium.The aggregate also preferably includes about 50% of potassic feldspar(or components which will become potassic feldspar when subjected to akilning temperature of about 1120° C.), about 30% of quartz (SiO₄), andabout 20% of non-organic volatile components which evolve (i.e., sublimeand/or vaporize) at a kilning temperature of between about 1120° C. andabout 1135° C. The aggregate is preferably crushed and/or ground to amean particle size of fine sand, and more particularly to a size whereabout 80% or more of the particles will pass through a 200 mesh (about0.074 mm) screen. Further, the aggregate is preferably not pre-processedby kilning (as described above with respect to methods for making porousmineral based granular material), thus leaving metal sulfides on thesurfaces of the particles (granules) which can sublimate and/or vaporizeduring kilning of the starting materials (as described in the paragraphabove). I have also determined that micaceous quartzite, sericitizedgranite and/or seriticized rhyolite which is processed by crushing,grinding, pulverizing, etc. to the preferred particle size tends toresult in somewhat elongate particles having a ratio of depth (minimumparticle dimension) to length (maximum particle dimension) of about 1:3.(The width of such particles tends to be greater than the depth, andless than the length.) I have also determined that once the processedaggregate is mixed with the cementing agent, the aggregate particlestend to align with one another in a first dimension which is parallel tothe major length dimension of the aggregate particles, with particles ofthe cementing agent being generally interspersed between the aggregateparticles.

The cementing agent used in this alternative method is preferablyPortland cement. The amount of cementing agent to be used is preferablyless than about 10% (by weight) of the total mass of the startingmaterials, and more preferably between about 3% and 7% (by weight) ofthe total mass of the starting materials (including the water componentthereof). It will be appreciated that the amount of cementing agentrequired to form the unitized formed mineral-based constructionmaterials according to this method (i.e., less than about 10% by weight)is less than the amount of cement typically used to form concrete(typically, about 10 to 15 percent cement, 60 to 75 percent aggregateand 15 to 20 percent water).

In preparing the starting materials for unitized formed mineral-basedconstruction materials manufactured according to the current alternativemethod (i.e., no separate sublimation agent is added to the startingmaterials), the aggregate and the cementing agent can be first mixedwith one another to obtain a generally homogeneous distribution of theparticles. Then the water can be added and mixed with the mixture of theaggregate and the cementing agent. (The amount of water to be added isas described above with respect to previously described methods forforming the unitized construction materials of the present disclosure).The resulting mixture of aggregate, cementing-agent and water can thenbe formed by placing the mixture into molds, or extruded (as describedherein), to achieve the desired form of the end product. The formedmixture of the starting materials are then cured (in accordance withprocedures described herein above) to allow the cementing agent toundergo the hydration process which results in a solidified unit of thestarting materials, which can then be placed into a kiln.

The mixed, formed and cured starting materials are then placed into akiln and subjected to a kilning temperature of between about 1100° C.and about 1135° C. (about 2025° F. and about 2075° F.) for a period oftime selected to allow micaceous components in the aggregate to evolveto felspathic components, and then for the felspathic components bealtered to remove metal sulfides present in the aggregate and cement,and also allow removal and/or conversion of calcium components from thecement into less reactive compounds (all as described above). Thetemperature regimen (i.e., temperature increase rate in the kiln,processing temperature, and processing time) can all be performedaccording to the parameters described above with respect to methodspreviously described herein for the manufacture of mineral-basedunitized construction materials.

As described above, the present disclosure provides for a method formanufacturing (i.e., making) unitized formed mineral-based constructionmaterials which includes the following steps: (i) providing startingmaterials comprising an aggregate, a cementing agent, and water; (ii)mixing the starting materials with one another to achieve a mixture ofthe starting materials; (iii) placing the mixture of the startingmaterials into a form (or mold); (iv) curing the mixture of startingmaterials in the form for a period of time selected to allow the mixtureof starting materials to become a solidified unit of the mixture ofstarting materials, the solidified unit of the mixture of startingmaterials being defined by a minimum dimension of thickness, length,width or diameter; (v) removing the consolidated unit of the mixture ofstarting materials from the form; (vi) placing the solidified unit ofthe mixture of starting materials into a kiln; (vii) heating the kilncontaining the solidified unit of the mixture of starting materials to aprocessing temperature of between about 1100° C. and about 1135° C. andmaintaining the kiln at the processing temperature for a period of timeof between about 10 minutes and 60 minutes per centimeter of the minimumdimension of the consolidated unit of the mixture of starting materials;and (viii) removing the solidified unit of the mixture of startingmaterials from the kiln. (It will be appreciated that the process asjust described can include additional and alternate steps describedherein, as well as variations on the recited steps.)

Manufacture of Porous Unitized Construction Materials from NativeMicaceous-Containing Rock.

In yet another embodiment I have discovered that porous unitizedconstruction materials can be fabricated from nativemicaceous-containing rock. In this embodiment units of the constructionmaterials are first cut from native micaceous-containing rock.Preferably, the native micaceous-containing rock contains at least 30%of micaceous material, and 30% of quartzitic material. Sericitizedrhyolites and granites can also be used. The units of the constructionmaterials can be cut from the native rock using known cutting processes,including water jet cutting, saw cutting, and laser cutting. Once cut tothe desired dimensions and shape, the cut units of the nativemicaceous-containing rock can be placed into a kiln and subjected to atemperature of between about 1000° C. and about 1200° C. for a period oftime of between about 6 minutes and 15 minutes per centimeter of themaximum dimension of the cut units. During this kilning processmicaceous components within the cut units of the native rock will evolveto felspathic components, and metal sulfides and other components willbe sublimated and/or vaporized, thus creating porous openings andpermeable channels within the cut units of the native rock. Theresulting (i.e., post-kilned) units will be unitized constructionmaterials having high strength and high porosity.

Examples of Uses for Unitized Construction Materials.

The present disclosure also provides for unitized formed mineral-basedconstruction materials manufactured according to the methods providedfor herein. When the unitized construction materials provided for hereinare manufactured with high porosity and permeability, these materialscan be used in the following exemplary applications: (i) as pavers forwalkways, roads, or any ground surface area where it is desirable toprovide a surface covering which provides for water permeability andwater retention; (ii) as roofing tiles to enable water to move throughthe tiles to a water runoff containment means; (iii) as flooring tilesto enable liquids imposed on the flooring tiles to move through thetiles to a liquid runoff containment means; (iv) as a leach pad for amineral leaching process; and (v) as a liquid filtration means to removesolids from liquids (e.g., to remove solids from water). When theunitized construction materials provided for herein are manufacturedwith low porosity and low permeability, these materials can be used asstructural elements (such as beams and other structural elements) and/orarchitectural units (such as facing bricks or as pavers). Further, theunitized construction materials provided for herein can be provided withhigh porosity (coupled with high or low permeability), and thus used aswall elements (or other construction elements) which are highlyreceptive to applied materials (such as paint or the like), as well asbeing used as light weight structural members.

I have further discovered that when the unitized construction materialsprovided for herein are manufactured to be liquid permeable (as providedfor by designed-in liquid permeability), the movement of liquidsthere-through can be inhibited by surface tension of the liquids at thesurfaces of the unitized construction materials. For example, when apaver formed as a unitized construction material provided for herein isdesigned with high permeability, a liquid presented on an upper surfaceof such a unitized construction material will generally not pass from acorresponding lower surface unless a means is provided to break surfacetension of the liquid at the lower surface. One means for breakingsurface tension of the liquid at the lower surface of the unitizedconstruction material is by placing the lower surface of the unitizedconstruction material into contact with a fluid conductive material thatwill facilitate movement of liquids within the unitized constructionmaterial into a substrate material. Examples of such a fluid conductivematerial include (i) the porous mineral-based granular material providedfor herein above; and (ii) a geotextile fabric. Examples of a substratematerial include: (i) the porous mineral-based granular materialprovided for herein above; and (ii) an aggregate material such as sandand/or gravel. Another means for breaking surface tension of the liquidat the lower surface of the unitized construction material is by placingthe unitized construction material at an angle (relative to a horizontalplane), or by forming angled divots on the lower surface of the unitizedconstruction material, which will promote movement of the liquid acrossthe lower surface of the unitized construction material, thus breakingsurface tension of the liquid at the lower surface of the unitizedconstruction material and allowing the liquid to move through the liquidpermeable unitized construction material.

Water Extraction Inserts in Low Permeability Surface Coverings.

Many surface coverings such as concrete (e.g., sidewalks, slabs, etc.),asphalt (e.g., streets) and bricks (e.g., courtyards, etc.) arecharacterized by generally very low permeability to water and otherfluids. An important consideration in many such surface coverings is theability to remove water (such as rainwater) from the surface in a quickmanner. To this end, most such surface coverings are installed with aslope which drains runoff to a water collection point. A common exampleis draining streets and sidewalks to storm drains. As indicate above,this storm water can be difficult to manage using existing sewagetreatment facilities, or may require an entirely separate storm watertreatment facility. A preferred solution to managing the storm waterrunoff is for the storm water to be conducted into the subgrade beneaththe surface. I have discovered a method for managing storm water (andother liquid) runoff from a generally impermeable grade surface whichresults in the water being conducted into a subgrade zone beneath thegrade surface. This method is particularly useful for retrofittingexisting impermeable grade surfaces. The method includes inserting azone of permeable tiles within, and through, the impermeable surfacecovering. When the method is used for retrofitting existing impermeablegrade surfaces, then the existing grade surface can be cut (e.g., usinga concrete saw, water cutting, etc.) to create an opening for insertingthe zone of permeable tiles. When the method is used in newconstruction, then the permeable tiles can be laid adjacent to an edgein the impermeable surface covering. The permeable tiles can beinstalled after new construction by providing block-outs for thepermeable tiles during construction. Examples of the method will bedescribed below with respect to FIGS. 5 through 8. Preferably, thepermeable tiles are arranged in a line across, or at an edge of, theimpermeable surface covering, and which is arranged to intercept liquidrunoff from the surface covering. The permeable tiles can bebrick-shaped, or other shapes as dictated by a particular application.The inclusion of one or more zones of permeable tiles within a surfacecovering is most advantageous when the permeable tiles, and indeed thesurface covering as a whole, is located over a subgrade bed of permeablematerial which can hold a volume of water. Common forms of subgrade fillwhich can hold water include aggregate such as gravel, sand and crushedrock. The porous mineral-based sand provided for hereinabove is aparticularly useful form of subsurface fill material that can be used inthis particular method, due not only to the large volume of water thatcan be accommodated by the pores, but also due to the fact that thepores tends to hold the water within the grains of the granular materialso that the water is released slowly therefrom. The frequency of thezones of permeable tiles (if more than one line or zone is to be appliedto a particular area), and the kind and volume of subgrade fill materialto be used, can be selected based on known historical local storm data,and on the level of water management desired.

Turning to FIG. 5, a surface covering system 300 is depicted in apartial side sectional view. The surface covering system 300 includes agenerally impermeable surface covering 302 (such as concrete, pavementor paving tiles) and a permeable tile 304 is inserted into a gap (notnumbered) which is formed in and through the generally impermeablesurface covering 302. (In this instance, the term “generallyimpermeable” means that the surface covering 302 has a permeability towater that is no more than 30% of the permeability of the permeable tile304.) The generally impermeable surface covering 302 and the permeabletile 304 are supported on a subgrade bed of fill material 306. Thepermeable tile 304 can be recessed below the upper surface 305 of thegenerally impermeable surface covering 302 in order to reduce wear onthe tile 304. Further, the edges of the generally impermeable surfacecovering 302 can be provided with rounded edges 308 to resist chippingand spalling of the surface covering 302 near the permeable tile 304. Agap 310 can be provided on either side of the permeable tile 304 tofacilitate installation of the tile 304 into the opening in the surfacecovering 302. The gap 310 can be filled with sand or grout in order tohold the permeable tile 304 in place between the portions of thegenerally impermeable surface covering 302 on either side of thepermeable tile 304. The installation depicted in FIG. 5 is particularlyuseful when the permeable tiles 304 are inserted into a preexistinggenerally impermeable surface covering 302 (as for example, when theopening for the permeable tiles 304 is formed in the generallyimpermeable surface covering 302 after the surface covering has been putin place).

FIG. 6 is a partial side sectional view of a surface covering system300A, which generally corresponds to the arrangement depicted in FIG. 5,but with the following differences. In FIG. 6 the permeable tile 304A iswedge-shaped, and a sand or other fill material 312 is provided in thegap (310 of FIG. 5) between the sides of the tile 304A and the sides ofthe opening in and through the generally impermeable surface covering302. In the arrangement depicted in FIG. 6 the wedge-shape of thepermeable tile 304A, and the fill material 312, assist in holding thetile 304A in place over the subgrade bed of fill material 306. In FIG. 6the angle of the wedge-shape of the permeable tile 304A, and the widthof the gap (310 of FIG. 5), are exaggerated for purposes ofillustration.

FIG. 7 is a partial side sectional view of a surface covering system300B, which is similar to the surface covering system 300 depicted inFIG. 5. In FIG. 7 a generally rigid geotextile fabric 314 is placedbeneath the permeable tile 304, and immediately on top of the subgradefill material 306. The geotextile fabric 314 is water permeable, but isalso selected to prevent fine material (such as silt and dirt) frompassing through the geotextile fabric 314 and into the subgrade fillmaterial 306. This will reduce the rate at which such fines caninfiltrate through the gap 310 (as well as through the permeable tile304) and clog the subgrade fill material 306. As depicted, thegeotextile fabric 314 is preferably installed so as to partially extendunder the edges of the generally impermeable surface covering 302 whichare adjacent to the permeable tile 304. In one variation the geotextilefabric 314 can be attached to the permeable tile 304 prior toinstallation of the tile 304. One method for attaching the geotextilefabric 314 to the permeable tile 304 is by stitch-gluing, which reducesthe presence of glue on the lower surface of the tile 304 (appreciatingthat glue on surfaces of the permeable tile can inhibit inflow of liquidinto and from the tile). Further, the gaps 310 can be filled with a fillmaterial (e.g., 312 of FIG. 6, described above), in which case it isintended that the fill material in the gaps will over time trap dirt,silt and other materials, thus making the fill material generallyimpermeable to water flow. This will consequently direct water flow(including any entrained solids) to the upper surface (not numbered) ofthe permeable tile 304, allowing water to move through the generallymicroscopic pores of the permeable tile, while leaving generallymacroscopic solids on the upper surface of the tile. This will preventthe migration of macroscopic solids into the subgrade material 306, thusreducing the likelihood of the subgrade material becoming clogged overtime. Any microscopic solids in the water flowing to the upper surfaceof the tiles 304 will thus tend to migrate through the permeable tiles,as well as the subgrade material 306, thus ensuring a long fluid-flowlife for both the permeable tiles 304 and the subgrade fill material306. Further, holes or other openings can be formed in the geotextilefabric 314 where the geotextile fabric is in contact with, or is inclose proximity to, the lower surface (not numbered) of the permeabletile 304, to thus ensure that the geotextile fabric does not present abarrier to water flow from the permeable tile 304 into the substrate306. Also, the geotextile fabric 314 can be attached to the permeabletiles 304 by a continuous, water impermeable glue strip at the outeredges of the lower surface (not numbered) of the tiles 304 in order toreduce initial flow of macroscopic entrained solids passing through thegap filling material (312, FIG. 6) and subsequently passing into theportion of the geotextile fabric which is directly beneath the lowersurface (not numbered) of the permeable tile. In general, the objectiveis to provide a system which provides a seal to migration of macroscopicsolids into the subgrade material 306, and this can be accomplished byway of the gap filling material (312, FIG. 6) becoming clogged during aperiod of initial use, the impermeability of the surface covering 302,and the microscopic porosity of the permeable tiles 304.

FIG. 8 is a plan view of a surface covering system 300C, which issimilar to the surface covering system 300 depicted in FIG. 5. In FIG. 8the permeable tiles 304C are provided with indentations 316 which areconfigured to receive projections 318 formed on the edges of thegenerally impermeable surface covering 302C. The indentations 316 andthe projections 318 act together as a locking system to lock the tiles304C into horizontal position with respect to the impermeable surfacecovering 302C. The arrangement depicted in FIG. 8 is particularly usefulwhen the impermeable surface covering 302C proximate the permeable tiles304C is formed from tiles or other materials which allow for theprojections 318 to be formed in relatively precise positions to ensureengagement with the indentations 316 in the permeable tiles 304C. Itwill be appreciated that the projections 318 can be formed on thepermeable tiles 304C, and the indentations 316 formed on the edges ofthe impermeable surface covering 302C. FIG. 8 also depicts a small gap310C between the edges of the permeable tiles 304C and the edges of theimpermeable surface covering 302C. The gap 310C allows for accommodationof slight variances in the relative positions of the indentations 316and the projections 318 with respect to one another. The gaps 310C canbe later filled with sand or other filling material in the mannerdescribed above with respect to FIG. 6. It will also be appreciated thatthe permeable tiles 304C can be provided with the geotextile fabric 314described above with respect to FIG. 7.

FIG. 9 is a partial side sectional view of a surface covering system300D, which is similar to the surface covering system 300 depicted inFIG. 5. However, in FIG. 9 the upper surface (not numbered) of thepermeable tile 304D includes a concave center section 320 which isbordered by generally flat sections 322. As depicted in FIG. 9, thegenerally flat sections 322 of the upper surface of the permeable tile304D are located below the upper surfaces 305 of the generallyimpermeable surface covering 302. However, the generally flat sections322 of the upper surface of the permeable tile 304D can also be alignedwith the upper surfaces 305 of the generally impermeable surfacecovering 302. The benefit of providing the concave center section 320 inthe upper surface of the permeable tile 304D is that the concave centersection allows a certain amount of pooling of water to occur when theinflow-rate of water to the upper surface (not numbered) of thepermeable tile 304D exceeds the rate at which water can pass through thepermeable tile to the subgrade fill material 306. Further, the benefitof providing the generally flat sections 322 on the upper surface of thepermeable tile 304D is to avoid a sharp corner at the outer edges (notnumbered) of the upper surface (also not numbered), since sharp cornersat the upper edges of the permeable tile 304D can potentially spall,thus presenting a rough edge. The arrangement presented in FIG. 9 isthus configured to allow for ease of movement of wheeled conveyances(such as wheelchairs and the like) over the upper surfaces of thegenerally impermeable surface covering 302 and the permeable tile 304D.Preferably the permeable tile 304D is installed in such a manner thatthe generally flat sections 322 on the upper surface of the tile arerecessed slightly below the upper surfaces (not numbered) of theimpermeable surface covering 302. This arrangement provides a residencepooling capacity for storm water (or other liquids) consisting of ageometric pooling volume (the volume of the concave section 320 belowthe generally flat sections 322) and an inset pooling volume (the volumebelow the upper surfaces of the impermeable surface covering, andexcluding the geometric volume).

It will also be appreciated an additional benefit is derived byinstalling the permeable tiles 304 (and variations thereof, as presentedabove) in a manner which permits removal of the permeable tiles withoutcompromising the integrity of the adjacent generally impermeable surfacecovering 302. (That is, permeable tiles 304 can be easily removed byvirtue of the gap 310 (FIG. 5) when the gap is filled with a materialwhich does not bond the permeable tile 304 to the generally impermeablesurface covering 302). The aforementioned benefit is that, should thepermeable tile 304 lose permeability due to influx of solids, then thepermeable tile 304 can be easily removed and replaced with a newpermeable tile (or cleaned and reinstalled).

FIG. 10 is a partial side sectional view of yet another surface coveringsystem 400. The surface covering system 400 is particularly useful inurban settings to remove runoff water (such as storm water) fromsidewalks and streets and to direct the water into a subgrade fill(versus the water flowing into a storm drain or the like). FIG. 11 is aplan view of the partial section depicted in FIG. 10. FIGS. 10 and 11will be discussed together. In the system 400 a row of permeable tiles304D (as described above with respect to FIG. 9) is placed at one sideof a generally impermeable sidewalk surface 402. Another row of thepermeable tiles 304D can be placed at the other side (not shown) of thesidewalk 402, and permeable tiles can also be inserted through thesidewalk between the distal sides thereof. Also, two rows of thepermeable tiles 304D can be placed adjacent to one another at the edgeof the sidewalk 402. The number of rows of permeable tiles 304D to beused to drain water from the sidewalk 402 can be calculated based onanticipated rainfall amounts (in inches per hour), and drainage rate ofthe tiles 304D, and the surface area of the sidewalk. The row ofpermeable tiles 304D can be located between the edge of the sidewalk 402and a curbing 404. To the left of the curbing (in FIGS. 10 and 11) is astreet surface 408, which is also generally impermeable. Another row ofimpermeable tiles 304D is placed adjacent to the curb 404, and a fillmaterial 410 (similar to fill material 312 of FIG. 6, described above)can be packed between the curbing 404 and the row of tiles 304D adjacentthe curbing. The fill material 410 can be sand or the like, and isintended to become generally impermeable over a short period of time.This will reduce the migration of fines into the permeable subgradematerial 406. The fine porosity of the permeable tiles 304D will preventparticles which can reduce permeability of the subgrade material 406from migrating into the subgrade material via the tiles 304D. As withthe permeable tiles placed adjacent to the sidewalk 402, a second row ofpermeable tiles can be placed adjacent to the curbing 404 on thestreet-side of the system 400. However, since vehicles may travel andpark adjacent to the curbing 404, it is desirable to avoid having thewheel loads of vehicles rest directly on the permeable tiles 304D.Accordingly, as depicted in FIG. 11, a second set of permeable tiles304D can be intermittently and orthogonally placed adjacent to thestreet-side row of permeable tiles 304D. As can be seen in FIG. 11, theorthogonally oriented permeable tiles 304D are placed between generallyimpermeable paver tiles 412. The paver tiles 412 can have highcompressive strength to resist vehicle wheel loads. Also, as depicted inFIG. 10, the orthogonally oriented permeable tiles 304D can be placedslightly below the paver tiles 412 (in the manner indicated in FIG. 9).In this way vehicles tires will tend to be supported by the paver tiles412, thus avoiding the imposition of significant loads on the permeabletiles 304D that are placed between the street surface 408 and thecurbing 404. The width of the permeable tiles 304D can be about 4 cm orless, such that vehicle tires (which typically have widths greater thanabout 12 cm) are generally suspended above the permeable tiles that areimmediately adjacent to the curbing 404. While not shown in FIGS. 10 and11, another row of permeable tiles can be inserted into the streetsurface 408 as a centerline, which can assist in removing water from thestreet surface.

Water Extraction Covering Over a Low Permeability Surface Covering.

It has now become a common practice to replace asphalt road surfacecoverings at high-traffic intersections with a concrete road surfacecovering. A concrete road surface covering is much more resistant thanis asphalt to the high level of braking and acceleration forces imposedupon the road at such high-traffic intersections. However, a concreteroad surface is generally impermeable to water, and thus presents theopportunity for a surface layer of water to accumulate upon the concreteroad surface, thus reducing stopping and accelerating capabilities forvehicles. Even with proper grading to promote migration of water fromthe concrete road surface there can still be a sheet of water movingacross the concrete road surface which inhibits braking and accelerationof vehicles. Accordingly, one use of the permeable unitized constructionmaterials of the present disclosure is to apply a layer of the permeableunitized construction materials of the present disclosure over the uppersurface of a concrete road surface at high-traffic intersections. Byproper grading of the intersection, water passing through the permeableunitized construction materials of the present disclosure can bechanneled from the underlying concrete road surface into water drainagechannels. Further, the overlying permeable unitized constructionmaterials can be provided with a selected degree of roughness tofacilitate braking and acceleration of vehicles thereon.

Third Embodiment: Recovery of Metals from Kilning of Mineral BasedMaterials

I have also discovered that the kilning of mineral-based components(such as micaceous-based and arkose-based rock) to produce the porousmineral-based granular materials provided for herein-above, and thekilning of sublimation-agent containing materials to form the unitizedformed construction materials provided for herein-above, results in theevolution of mineral-containing gasses which can be subsequentlyprocessed in order to recover the mineral content of suchmineral-containing gasses, as provided for more fully below.

Recovery of Metals from Kilning of Micaceous-Based and Arkose-BasedRock.

When micaceous-based and arkose-based rock is kilned at a temperature ofbetween about 1000° C. and about 1250° C. (about 1830-2280° F.), thekilning will result in the evolution (by sublimation and/orvaporization) of metal sulfides (such as zinc sulfide and iron sulfide)in a gaseous form. The gaseous form of these evolved metal sulfides canbe collected and condensed into a solid form, and subsequently processed(by known means for separating metallic elements from sulfur) in orderto extract the mineral content from the condensed gasses evolved duringkilning of the arkose-based rock. (A similar metal recovery process canbe used when manufactured mineral materials are used as the startingmaterial for the porous mineral-based granular materials provided forherein-above.)

Recovery of Metals from Kilning of Starting Materials for UnitizedConstruction Materials as Provided for Herein.

When the starting materials for a unitized construction material (asprovided for herein-above) are kilned, the kilning process will generategaseous metallic components which include a significant gaseous portionof the sublimation agent (as described above), and/or gaseous metalliccomponents released by the sublimation agent. These gaseous metalliccomponents can be collected and condensed, and subsequently processed(using known methods for separating metallic components from metallicsulfides and metallic oxides) in order to recover metallic components,and in particular the metallic components of the sublimation agent andmetallic components of the aggregate. Accordingly, a large portion(e.g., 50% or more) of the evolved metallic components can be recovered.These recovered metallic components can then be used in other industrialprocesses.

Method for Recovering Metals Generated by Kilning of Mineral-Based andMineral-Containing Material.

As described above, mineral containing gasses are evolved (either viasublimation and/or vaporization) when mineral-based and/ormineral-containing materials are kilned at a temperature of betweenabout 1200° C. and about 1300° C. (about 2200-2400° F.). A method forrecovering metals generated by kilning of mineral-based and/ormineral-containing materials at a temperature of between about 1200° C.and about 1300° C. thus includes the following steps: (i) placing astarting material comprising a mineral-based and/or a mineral-containingmaterial into a kiln (e.g., as sand or as a solidified precursor unitfor a unitized formed construction material, as described above): (ii)heating the starting material in the kiln to a temperature of betweenabout 1200° C. and about 1300° C.; (iii) recovering and condensingmetallic-containing gasses evolved from the starting material in orderto obtain condensed metallic compounds evolved from the startingmaterial; and (iv) processing the condensed metallic compounds evolvedfrom the starting material in order to extract the metallic contenttherefrom.

Use of Relative Terminology in the Above Description.

The use of relative terminology in the above disclosure (e.g., the useof terms such as “about”, “essentially”, “substantially”, etc., as usedherein above) are to be interpreted in light of the desired objectivesto be accomplished (as recited herein). For example, the above-recitedsintering temperatures, sublimation temperatures, sintering times,sublimation times, and percentages of material composition can all bevaried (as described above) in order to achieve the recited levels ofsublimation and/or sintering in order to achieve the desired levels ofporosity and/or sintering for the desired end product of eithermineral-based porous granular materials and/or mineral-basedconstruction materials. While not specifically limiting any of theabove-described time, temperature and/or composition limitations, it isgenerally considered that any relative term used herein will constitutea practical limit beyond which the recited objectives will not beachieved. For example, for a recited lower temperature range of “about”1200° C., that would include a lower temperature as low as 3% of 1200°C. (which is 40° C.), and thus a lower temperature of 1160° C. isconsidered to be in the range of “about” 1200° C. More specifically: (i)when referring to preferred temperatures recited herein, relativeterminology is intended to mean temperatures within 3% of the recitedquantity; (ii) when referring to preferred times recited herein,relative terminology is intended to mean times within 10% of the recitedquantity; and (iii) when referring to preferred compositions of matterrecited herein, relative terminology is intended to mean compositions ofmatter within 15% of the recited quantity (or quantities). However,these indicated limitations are not to be considered as strictlimitations, and it is the end-objective for any article of manufacture,or methods for making such articles of manufacture, as provided forherein, that are to be considered as limitations on recited quantities,all as within the scope of the concept of equivalents and the currentdisclosure. As also described above, various combinations of thestarting materials can be used in manufacturing the desired end products(and in particular, combinations of different kinds of aggregate, anddifferent kinds of sublimation agents (for the unitized constructionmaterials), and thus the kilning temperatures and kilning times caninclude respective overlapping ranges (as well as their allowedvariances) to thus result in an engineered finished product havingpreselected desired properties (and in particular, porosity,permeability and/or strength).

The preceding description has been presented only to illustrate anddescribe exemplary methods and apparatus of the present disclosure. Itis not intended to be exhaustive or to limit the disclosure to anyprecise form disclosed. Many modifications and variations are possiblein light of the above teachings. It is intended that the scope of one ormore inventions provided for herein be defined at least by the followingclaims.

I claim:
 1. A method to manufacture a mineral-based porous granular material, comprising: providing a starting material comprising at least 70% by weight of a micaceous arkose rock material, and wherein: the starting material is in a granular form; and at least about 50% by volume of the starting material has a mean diameter of between about 0.060 mm and about 0.65 mm; placing the starting material into a bed on a support surface; placing the support surface containing the bed of the starting material into a kiln; subjecting the bed of starting material within the kiln to a basic processing temperature of between about 1100° C. and about 1300° C. for a basic processing temperature processing time selected to transform at least 40% by weight of micaceous components in the micaceous arkose rock material into feldspar containing metal sulfides, and to evolve at least 30 percent by volume of the metal sulfides within the feldspar from the feldspar as metallic oxides; and thereafter cooling the kilned starting material to an ambient temperature.
 2. The method of claim 1 and wherein the micaceous arkose rock material comprises between about 10% and 40% by weight of quartz, and between about 20% and 40% by weight of metallic compounds.
 3. The method of claim 1 and wherein the feldspar is at least about 80% or more by volume of a sodic felsic material, a potassic felsic material, or a combination thereof.
 4. The method of claim 1 and wherein about 60% by volume of the starting material has a mean diameter of between about 0.10 mm and 0.4 mm.
 5. The method of claim 1 and wherein the feldspar comprises at least about 20% by weight of the metal sulfides.
 6. The method of claim 1 and wherein the step of providing the starting material includes one or more of performing a crushing process, a grinding process, and a screening process, to facilitate in obtaining the mean diameter of the starting materials of between about 0.060 mm and about 0.65 mm.
 7. The method of claim 1 and wherein the step of providing the starting material includes one or more of performing a washing process and a leaching process to facilitate in obtaining the mean diameter of the starting material of between about 0.060 mm and about 0.65 mm.
 8. The method of claim 1 and further comprising, subsequent to placing the support surface containing the bed of the starting material into the kiln, and prior to subjecting the bed of starting material within the kiln to the basic processing temperature, increasing the kiln from a starting temperature to the basic processing temperature.
 9. The method of claim 8 and wherein: the bed of starting material is defined by a bed thickness; and the kiln is increased from the starting temperature to the basic processing temperature at a rate of between about 2 minutes and about 6 minutes per centimeter of bed thickness.
 10. The method of claim 9 and wherein: the starting temperature of the kiln is less than about 200° C.; and prior to increasing the kiln from the starting temperature to the basic processing temperature, the kiln is held at the starting temperature for a period of between about 10 minutes and about 20 minutes per centimeter of bed thickness.
 11. The method of claim 1 and wherein the bed of starting material is defined by a bed thickness, and the basic processing temperature processing time is between about 15 minutes and about 30 minutes for each centimeter of the bed thickness.
 12. The method of claim 1 and wherein: following subjecting the bed of starting material within the kiln to the basic processing temperature for the basic processing temperature processing time the starting material becomes a kilned starting material; the method further comprising one or more of crushing and grinding the kilned starting material into a granular form of the kilned starting material.
 13. The method of claim 1 and: wherein, following subjecting the bed of starting material within the kiln to the basic processing temperature for the basic processing temperature processing time the starting material becomes a kilned starting material; the method further comprising: one or more of crushing and grinding the kilned starting material into a granular form of the kilned starting material; using the kilned starting material as at least part of a secondary starting material; and placing the secondary starting material into the kiln at the basic processing temperature for the basic processing temperature processing time.
 14. The method of claim 1 and wherein the metal sulfide components evolved during the step of subjecting the bed of starting material within the kiln to the basic processing temperature for the basic processing temperature processing time are evolved in a gaseous form, the method further comprising collecting and condensing the gaseous form of the evolved metal sulfides as recovered metal sulfides, and processing the recovered metal sulfides to extract at least one metallic component therefrom.
 15. A method for manufacturing a mineral-based porous granular material, comprising: providing a starting material comprising at least 70% of a arkose rock based material, and wherein: the starting material is in a granular form; at least about 50% by volume of the arkose rock based material has a mean diameter of between about 0.10 mm and about 0.60 mm; and the arkose rock based material comprises between about 20% and 50% by weight of micaceous material, between about 10% and 40% by weight of quartz, and at least about 20% of metallic compounds; placing the starting material into a bed on a support surface; placing the support surface containing the bed of the starting material into a kiln; subjecting the bed of starting material within the kiln to a basic processing temperature of greater than 900° C. for a basic processing temperature processing time selected to cause the micaceous material to evolve into a form comprising a feldspar and a metal silicate, thus forming pores at least on outer surfaces of the starting material; and thereafter cooling the starting material to an ambient temperature.
 16. The method of claim 15 and wherein the micaceous material is in the form of muscovite.
 17. The method of claim 15 and wherein the micaceous material is in the form of paragonite.
 18. The method of claim 15 and wherein the micaceous material is defined by a particle size having a major dimension of less than 10⁻⁸ meters.
 19. The method of claim 15, and: wherein, following subjecting the bed of starting material within the kiln to the basic processing temperature for the basic processing temperature processing time the starting material becomes a kilned starting material; the method further comprising: one or more of crushing and grinding the kilned starting material into a granular form of the kilned starting material; using the kilned starting material as at least part of a secondary starting material; and placing the secondary starting material into the kiln at the basic processing temperature for the basic processing temperature processing time.
 20. A mineral-based porous granular material manufactured according to the method of claim
 15. 